diff --git a/UPGRADE.md b/UPGRADE.md
index 8de79b7..d875329 100644
--- a/UPGRADE.md
+++ b/UPGRADE.md
@@ -1,5 +1,25 @@
 # Upgrade
 
+## Upgrade v0.7.x > v1.0.x
+
+### 1. Protected property and method naming
+In order to unify coding style, leading underscores were removed from all private and protected properties 
+and methods. 
+
+Example before the change:
+```php
+GraphQL\Schema::$_queryType
+```
+
+Correct usage after the change:
+```php
+GraphQL\Schema::$queryType
+```
+
+So if you rely on any protected properties or methods of any GraphQL class, make sure to 
+delete leading underscores.
+
+
 ## Upgrade v0.6.x > v0.7.x
 
 There are a few new breaking changes in v0.7.0 that were added to the graphql-js reference implementation 
diff --git a/src/Language/AST/Node.php b/src/Language/AST/Node.php
index 328dfdc..76a5b3b 100644
--- a/src/Language/AST/Node.php
+++ b/src/Language/AST/Node.php
@@ -76,7 +76,7 @@ abstract class Node
     const DIRECTIVE_DEFINITION = 'DirectiveDefinition';
 
     /**
-        type Node = Name
+      type Node = Name
     | Document
     | OperationDefinition
     | VariableDefinition
@@ -120,20 +120,24 @@ abstract class Node
      */
     public function cloneDeep()
     {
-        return $this->_cloneValue($this);
+        return $this->cloneValue($this);
     }
 
-    private function _cloneValue($value)
+    /**
+     * @param $value
+     * @return array|Node
+     */
+    private function cloneValue($value)
     {
         if (is_array($value)) {
             $cloned = [];
             foreach ($value as $key => $arrValue) {
-                $cloned[$key] = $this->_cloneValue($arrValue);
+                $cloned[$key] = $this->cloneValue($arrValue);
             }
         } else if ($value instanceof Node) {
             $cloned = clone $value;
             foreach (get_object_vars($cloned) as $prop => $propValue) {
-                $cloned->{$prop} = $this->_cloneValue($propValue);
+                $cloned->{$prop} = $this->cloneValue($propValue);
             }
         } else {
             $cloned = $value;
@@ -147,6 +151,11 @@ abstract class Node
      */
     public function __toString()
     {
-        return json_encode($this);
+        $tmp = (array) $this;
+        $tmp['loc'] = [
+            'start' => $this->loc->start,
+            'end' => $this->loc->end
+        ];
+        return json_encode($tmp);
     }
 }
diff --git a/src/Language/Parser.php b/src/Language/Parser.php
index 6a83a4a..514eae8 100644
--- a/src/Language/Parser.php
+++ b/src/Language/Parser.php
@@ -117,6 +117,11 @@ class Parser
      */
     private $lexer;
 
+    /**
+     * Parser constructor.
+     * @param Source $source
+     * @param array $options
+     */
     function __construct(Source $source, array $options = [])
     {
         $this->lexer = new Lexer($source, $options);
diff --git a/src/Schema.php b/src/Schema.php
index 5f488b4..83b05bd 100644
--- a/src/Schema.php
+++ b/src/Schema.php
@@ -11,42 +11,46 @@ use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Definition\WrappingType;
 use GraphQL\Type\Introspection;
 
+/**
+ * Class Schema
+ * @package GraphQL
+ */
 class Schema
 {
     /**
      * @var ObjectType
      */
-    protected $_queryType;
+    protected $queryType;
 
     /**
      * @var ObjectType
      */
-    protected $_mutationType;
+    protected $mutationType;
 
     /**
      * @var ObjectType
      */
-    protected $_subscriptionType;
+    protected $subscriptionType;
 
     /**
      * @var Directive[]
      */
-    protected $_directives;
+    protected $directives;
 
     /**
      * @var array<string, Type>
      */
-    protected $_typeMap;
+    protected $typeMap;
 
     /**
      * @var array<string, ObjectType[]>
      */
-    protected $_implementations;
+    protected $implementations;
 
     /**
      * @var array<string, array<string, boolean>>
      */
-    protected $_possibleTypeMap;
+    protected $possibleTypeMap;
 
     /**
      * Schema constructor.
@@ -69,10 +73,13 @@ class Schema
             ];
         }
 
-        $this->_init($config);
+        $this->init($config);
     }
 
-    protected function _init(array $config)
+    /**
+     * @param array $config
+     */
+    protected function init(array $config)
     {
         $config += [
             'query' => null,
@@ -88,19 +95,19 @@ class Schema
             "Schema query must be Object Type but got: " . Utils::getVariableType($config['query'])
         );
 
-        $this->_queryType = $config['query'];
+        $this->queryType = $config['query'];
 
         Utils::invariant(
             !$config['mutation'] || $config['mutation'] instanceof ObjectType,
             "Schema mutation must be Object Type if provided but got: " . Utils::getVariableType($config['mutation'])
         );
-        $this->_mutationType = $config['mutation'];
+        $this->mutationType = $config['mutation'];
 
         Utils::invariant(
             !$config['subscription'] || $config['subscription'] instanceof ObjectType,
             "Schema subscription must be Object Type if provided but got: " . Utils::getVariableType($config['subscription'])
         );
-        $this->_subscriptionType = $config['subscription'];
+        $this->subscriptionType = $config['subscription'];
 
         Utils::invariant(
             !$config['types'] || is_array($config['types']),
@@ -112,7 +119,7 @@ class Schema
             "Schema directives must be Directive[] if provided but got " . Utils::getVariableType($config['directives'])
         );
 
-        $this->_directives = array_merge($config['directives'], [
+        $this->directives = array_merge($config['directives'], [
             Directive::includeDirective(),
             Directive::skipDirective()
         ]);
@@ -129,16 +136,16 @@ class Schema
         }
 
         foreach ($initialTypes as $type) {
-            $this->_extractTypes($type);
+            $this->extractTypes($type);
         }
-        $this->_typeMap += Type::getInternalTypes();
+        $this->typeMap += Type::getInternalTypes();
 
         // Keep track of all implementations by interface name.
-        $this->_implementations = [];
-        foreach ($this->_typeMap as $typeName => $type) {
+        $this->implementations = [];
+        foreach ($this->typeMap as $typeName => $type) {
             if ($type instanceof ObjectType) {
                 foreach ($type->getInterfaces() as $iface) {
-                    $this->_implementations[$iface->name][] = $type;
+                    $this->implementations[$iface->name][] = $type;
                 }
             }
         }
@@ -149,7 +156,7 @@ class Schema
      */
     public function getQueryType()
     {
-        return $this->_queryType;
+        return $this->queryType;
     }
 
     /**
@@ -157,7 +164,7 @@ class Schema
      */
     public function getMutationType()
     {
-        return $this->_mutationType;
+        return $this->mutationType;
     }
 
     /**
@@ -165,7 +172,7 @@ class Schema
      */
     public function getSubscriptionType()
     {
-        return $this->_subscriptionType;
+        return $this->subscriptionType;
     }
 
     /**
@@ -173,7 +180,7 @@ class Schema
      */
     public function getTypeMap()
     {
-        return $this->_typeMap;
+        return $this->typeMap;
     }
 
     /**
@@ -196,7 +203,7 @@ class Schema
             return $abstractType->getTypes();
         }
         Utils::invariant($abstractType instanceof InterfaceType);
-        return isset($this->_implementations[$abstractType->name]) ? $this->_implementations[$abstractType->name] : [];
+        return isset($this->implementations[$abstractType->name]) ? $this->implementations[$abstractType->name] : [];
     }
 
     /**
@@ -206,19 +213,19 @@ class Schema
      */
     public function isPossibleType(AbstractType $abstractType, ObjectType $possibleType)
     {
-        if (null === $this->_possibleTypeMap) {
-            $this->_possibleTypeMap = [];
+        if (null === $this->possibleTypeMap) {
+            $this->possibleTypeMap = [];
         }
 
-        if (!isset($this->_possibleTypeMap[$abstractType->name])) {
+        if (!isset($this->possibleTypeMap[$abstractType->name])) {
             $tmp = [];
             foreach ($this->getPossibleTypes($abstractType) as $type) {
                 $tmp[$type->name] = true;
             }
-            $this->_possibleTypeMap[$abstractType->name] = $tmp;
+            $this->possibleTypeMap[$abstractType->name] = $tmp;
         }
 
-        return !empty($this->_possibleTypeMap[$abstractType->name][$possibleType->name]);
+        return !empty($this->possibleTypeMap[$abstractType->name][$possibleType->name]);
     }
 
     /**
@@ -226,7 +233,7 @@ class Schema
      */
     public function getDirectives()
     {
-        return $this->_directives;
+        return $this->directives;
     }
 
     /**
@@ -243,24 +250,39 @@ class Schema
         return null;
     }
 
+    /**
+     * @param $type
+     * @deprecated since 17.10.2016 in favor of $this->extractTypes
+     * @return array
+     */
     protected function _extractTypes($type)
+    {
+        trigger_error(__METHOD__ . ' is deprecated in favor of ' . __CLASS__ . '::extractTypes', E_USER_DEPRECATED);
+        return $this->extractTypes($type);
+    }
+
+    /**
+     * @param $type
+     * @return array
+     */
+    protected function extractTypes($type)
     {
         if (!$type) {
-            return $this->_typeMap;
+            return $this->typeMap;
         }
 
         if ($type instanceof WrappingType) {
-            return $this->_extractTypes($type->getWrappedType(true));
+            return $this->extractTypes($type->getWrappedType(true));
         }
 
-        if (!empty($this->_typeMap[$type->name])) {
+        if (!empty($this->typeMap[$type->name])) {
             Utils::invariant(
-                $this->_typeMap[$type->name] === $type,
+                $this->typeMap[$type->name] === $type,
                 "Schema must contain unique named types but contains multiple types named \"$type\"."
             );
-            return $this->_typeMap;
+            return $this->typeMap;
         }
-        $this->_typeMap[$type->name] = $type;
+        $this->typeMap[$type->name] = $type;
 
         $nestedTypes = [];
 
@@ -280,8 +302,8 @@ class Schema
             }
         }
         foreach ($nestedTypes as $type) {
-            $this->_extractTypes($type);
+            $this->extractTypes($type);
         }
-        return $this->_typeMap;
+        return $this->typeMap;
     }
 }
diff --git a/src/Type/Definition/AbstractType.php b/src/Type/Definition/AbstractType.php
index e0f56c1..97fa1c3 100644
--- a/src/Type/Definition/AbstractType.php
+++ b/src/Type/Definition/AbstractType.php
@@ -1,14 +1,13 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
-interface AbstractType
-{
 /*
 export type GraphQLAbstractType =
 GraphQLInterfaceType |
 GraphQLUnionType;
 */
+interface AbstractType
+{
     /**
      * @return callable|null
      */
diff --git a/src/Type/Definition/BooleanType.php b/src/Type/Definition/BooleanType.php
index 262b274..38e81e3 100644
--- a/src/Type/Definition/BooleanType.php
+++ b/src/Type/Definition/BooleanType.php
@@ -3,22 +3,44 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Language\AST\BooleanValue;
 
+/**
+ * Class BooleanType
+ * @package GraphQL\Type\Definition
+ */
 class BooleanType extends ScalarType
 {
+    /**
+     * @var string
+     */
     public $name = Type::BOOLEAN;
 
+    /**
+     * @var string
+     */
     public $description = 'The `Boolean` scalar type represents `true` or `false`.';
 
+    /**
+     * @param mixed $value
+     * @return bool
+     */
     public function serialize($value)
     {
         return !!$value;
     }
 
+    /**
+     * @param mixed $value
+     * @return bool
+     */
     public function parseValue($value)
     {
         return !!$value;
     }
 
+    /**
+     * @param $ast
+     * @return bool|null
+     */
     public function parseLiteral($ast)
     {
         if ($ast instanceof BooleanValue) {
diff --git a/src/Type/Definition/CompositeType.php b/src/Type/Definition/CompositeType.php
index 585b36d..dd8bdf8 100644
--- a/src/Type/Definition/CompositeType.php
+++ b/src/Type/Definition/CompositeType.php
@@ -1,13 +1,12 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
-interface CompositeType
-{
 /*
 export type GraphQLCompositeType =
 GraphQLObjectType |
 GraphQLInterfaceType |
 GraphQLUnionType;
 */
+interface CompositeType
+{
 }
diff --git a/src/Type/Definition/Config.php b/src/Type/Definition/Config.php
index e2b5660..024a9e5 100644
--- a/src/Type/Definition/Config.php
+++ b/src/Type/Definition/Config.php
@@ -3,6 +3,10 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Utils;
 
+/**
+ * Class Config
+ * @package GraphQL\Type\Definition
+ */
 class Config
 {
     const BOOLEAN = 1;
@@ -23,8 +27,14 @@ class Config
     const KEY_AS_NAME = 131072;
     const MAYBE_THUNK = 262144;
 
+    /**
+     * @var bool
+     */
     private static $enableValidation = false;
 
+    /**
+     * Disables config validation
+     */
     public static function disableValidation()
     {
         self::$enableValidation = false;
@@ -39,11 +49,15 @@ class Config
         self::$enableValidation = true;
     }
 
+    /**
+     * @param array $config
+     * @param array $definition
+     */
     public static function validate(array $config, array $definition)
     {
         if (self::$enableValidation) {
             $name = isset($config['name']) ? $config['name'] : 'UnnamedType';
-            self::_validateMap($name, $config, $definition);
+            self::validateMap($name, $config, $definition);
         }
     }
 
@@ -75,7 +89,13 @@ class Config
         return $tmp;
     }
 
-    private static function _validateMap($typeName, array $map, array $definitions, $pathStr = null)
+    /**
+     * @param $typeName
+     * @param array $map
+     * @param array $definitions
+     * @param null $pathStr
+     */
+    private static function validateMap($typeName, array $map, array $definitions, $pathStr = null)
     {
         $suffix = $pathStr ? " at $pathStr" : '';
 
@@ -87,17 +107,25 @@ class Config
         }
 
         // Make sure that all required keys are present in map
-        $requiredKeys = array_filter($definitions, function($def) {return (self::_getFlags($def) & self::REQUIRED) > 0;});
+        $requiredKeys = array_filter($definitions, function($def) {return (self::getFlags($def) & self::REQUIRED) > 0;});
         $missingKeys = array_keys(array_diff_key($requiredKeys, $map));
         Utils::invariant(empty($missingKeys), 'Error in "'.$typeName.'" type definition: Required keys missing: "%s"' . $suffix, implode(', ', $missingKeys));
 
         // Make sure that every map value is valid given the definition
         foreach ($map as $key => $value) {
-            self::_validateEntry($typeName, $key, $value, $definitions[$key], $pathStr ? "$pathStr:$key" : $key);
+            self::validateEntry($typeName, $key, $value, $definitions[$key], $pathStr ? "$pathStr:$key" : $key);
         }
     }
 
-    private static function _validateEntry($typeName, $key, $value, $def, $pathStr)
+    /**
+     * @param $typeName
+     * @param $key
+     * @param $value
+     * @param $def
+     * @param $pathStr
+     * @throws \Exception
+     */
+    private static function validateEntry($typeName, $key, $value, $def, $pathStr)
     {
         $type = Utils::getVariableType($value);
         $err = 'Error in "'.$typeName.'" type definition: expecting %s at "' . $pathStr . '", but got "' . $type . '"';
@@ -116,7 +144,7 @@ class Config
                 if ($def->flags & self::KEY_AS_NAME) {
                     $value += ['name' => $key];
                 }
-                self::_validateMap($typeName, $value, $def->definition, $pathStr);
+                self::validateMap($typeName, $value, $def->definition, $pathStr);
             } else if (!empty($def->isArray)) {
 
                 if ($def->flags & self::REQUIRED) {
@@ -132,9 +160,9 @@ class Config
                         if ($def->flags & self::KEY_AS_NAME) {
                             $arrValue += ['name' => $arrKey];
                         }
-                        self::_validateMap($typeName, $arrValue, $def->definition, "$pathStr:$arrKey");
+                        self::validateMap($typeName, $arrValue, $def->definition, "$pathStr:$arrKey");
                     } else {
-                        self::_validateEntry($typeName, $arrKey, $arrValue, $def->definition, "$pathStr:$arrKey");
+                        self::validateEntry($typeName, $arrKey, $arrValue, $def->definition, "$pathStr:$arrKey");
                     }
                 }
             } else {
@@ -209,7 +237,11 @@ class Config
         }
     }
 
-    private static function _getFlags($def)
+    /**
+     * @param $def
+     * @return mixed
+     */
+    private static function getFlags($def)
     {
         return is_object($def) ? $def->flags : $def;
     }
diff --git a/src/Type/Definition/CustomScalarType.php b/src/Type/Definition/CustomScalarType.php
index 0893c27..9446b9b 100644
--- a/src/Type/Definition/CustomScalarType.php
+++ b/src/Type/Definition/CustomScalarType.php
@@ -1,11 +1,21 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
+/**
+ * Class CustomScalarType
+ * @package GraphQL\Type\Definition
+ */
 class CustomScalarType extends ScalarType
 {
-    private $config;
+    /**
+     * @var array
+     */
+    public $config;
 
+    /**
+     * CustomScalarType constructor.
+     * @param array $config
+     */
     function __construct(array $config)
     {
         $this->name = $config['name'];
@@ -13,16 +23,28 @@ class CustomScalarType extends ScalarType
         parent::__construct();
     }
 
+    /**
+     * @param mixed $value
+     * @return mixed
+     */
     public function serialize($value)
     {
         return call_user_func($this->config['serialize'], $value);
     }
 
+    /**
+     * @param mixed $value
+     * @return mixed
+     */
     public function parseValue($value)
     {
         return call_user_func($this->config['parseValue'], $value);
     }
 
+    /**
+     * @param $valueAST
+     * @return mixed
+     */
     public function parseLiteral(/* GraphQL\Language\AST\Value */ $valueAST)
     {
         return call_user_func($this->config['parseLiteral'], $valueAST);
diff --git a/src/Type/Definition/Directive.php b/src/Type/Definition/Directive.php
index ae09422..d815dfa 100644
--- a/src/Type/Definition/Directive.php
+++ b/src/Type/Definition/Directive.php
@@ -1,10 +1,20 @@
 <?php
 namespace GraphQL\Type\Definition;
 
+/**
+ * Class Directive
+ * @package GraphQL\Type\Definition
+ */
 class Directive
 {
+    /**
+     * @var array
+     */
     public static $internalDirectives;
 
+    /**
+     * @var array
+     */
     public static $directiveLocations = [
         'QUERY' => 'QUERY',
         'MUTATION' => 'MUTATION',
@@ -33,6 +43,9 @@ class Directive
         return $internal['skip'];
     }
 
+    /**
+     * @return array
+     */
     public static function getInternalDirectives()
     {
         if (!self::$internalDirectives) {
@@ -96,6 +109,10 @@ class Directive
      */
     public $args;
 
+    /**
+     * Directive constructor.
+     * @param array $config
+     */
     public function __construct(array $config)
     {
         foreach ($config as $key => $value) {
diff --git a/src/Type/Definition/EnumType.php b/src/Type/Definition/EnumType.php
index 3767562..cd7ba22 100644
--- a/src/Type/Definition/EnumType.php
+++ b/src/Type/Definition/EnumType.php
@@ -4,22 +4,26 @@ namespace GraphQL\Type\Definition;
 use GraphQL\Language\AST\EnumValue;
 use GraphQL\Utils;
 
-class EnumType extends Type implements InputType, OutputType
+/**
+ * Class EnumType
+ * @package GraphQL\Type\Definition
+ */
+class EnumType extends Type implements InputType, OutputType, LeafType
 {
     /**
      * @var array<EnumValueDefinition>
      */
-    private $_values;
+    private $values;
 
     /**
      * @var \ArrayObject<mixed, EnumValueDefinition>
      */
-    private $_valueLookup;
+    private $valueLookup;
 
     /**
      * @var \ArrayObject<string, EnumValueDefinition>
      */
-    private $_nameLookup;
+    private $nameLookup;
 
     public function __construct($config)
     {
@@ -36,11 +40,11 @@ class EnumType extends Type implements InputType, OutputType
 
         $this->name = $config['name'];
         $this->description = isset($config['description']) ? $config['description'] : null;
-        $this->_values = [];
+        $this->values = [];
 
         if (!empty($config['values'])) {
             foreach ($config['values'] as $name => $value) {
-                $this->_values[] = Utils::assign(new EnumValueDefinition(), $value + ['name' => $name, 'value' => $name]); // value will be equal to name only if 'value'  is not set in definition
+                $this->values[] = Utils::assign(new EnumValueDefinition(), $value + ['name' => $name, 'value' => $name]); // value will be equal to name only if 'value'  is not set in definition
             }
         }
     }
@@ -50,7 +54,7 @@ class EnumType extends Type implements InputType, OutputType
      */
     public function getValues()
     {
-        return $this->_values;
+        return $this->values;
     }
 
     /**
@@ -59,7 +63,7 @@ class EnumType extends Type implements InputType, OutputType
      */
     public function serialize($value)
     {
-        $lookup = $this->_getValueLookup();
+        $lookup = $this->getValueLookup();
         return isset($lookup[$value]) ? $lookup[$value]->name : null;
     }
 
@@ -69,7 +73,7 @@ class EnumType extends Type implements InputType, OutputType
      */
     public function parseValue($value)
     {
-        $lookup = $this->_getNameLookup();
+        $lookup = $this->getNameLookup();
         return isset($lookup[$value]) ? $lookup[$value]->value : null;
     }
 
@@ -80,7 +84,7 @@ class EnumType extends Type implements InputType, OutputType
     public function parseLiteral($value)
     {
         if ($value instanceof EnumValue) {
-            $lookup = $this->_getNameLookup();
+            $lookup = $this->getNameLookup();
             if (isset($lookup[$value->value])) {
                 $enumValue = $lookup[$value->value];
                 if ($enumValue) {
@@ -95,31 +99,31 @@ class EnumType extends Type implements InputType, OutputType
      * @todo Value lookup for any type, not just scalars
      * @return \ArrayObject<mixed, EnumValueDefinition>
      */
-    protected function _getValueLookup()
+    private function getValueLookup()
     {
-        if (null === $this->_valueLookup) {
-            $this->_valueLookup = new \ArrayObject();
+        if (null === $this->valueLookup) {
+            $this->valueLookup = new \ArrayObject();
 
             foreach ($this->getValues() as $valueName => $value) {
-                $this->_valueLookup[$value->value] = $value;
+                $this->valueLookup[$value->value] = $value;
             }
         }
 
-        return $this->_valueLookup;
+        return $this->valueLookup;
     }
 
     /**
      * @return \ArrayObject<string, GraphQLEnumValueDefinition>
      */
-    protected function _getNameLookup()
+    private function getNameLookup()
     {
-        if (!$this->_nameLookup) {
+        if (!$this->nameLookup) {
             $lookup = new \ArrayObject();
             foreach ($this->getValues() as $value) {
                 $lookup[$value->name] = $value;
             }
-            $this->_nameLookup = $lookup;
+            $this->nameLookup = $lookup;
         }
-        return $this->_nameLookup;
+        return $this->nameLookup;
     }
 }
diff --git a/src/Type/Definition/EnumValueDefinition.php b/src/Type/Definition/EnumValueDefinition.php
index 7bf9ff9..2afc09a 100644
--- a/src/Type/Definition/EnumValueDefinition.php
+++ b/src/Type/Definition/EnumValueDefinition.php
@@ -1,6 +1,10 @@
 <?php
 namespace GraphQL\Type\Definition;
 
+/**
+ * Class EnumValueDefinition
+ * @package GraphQL\Type\Definition
+ */
 class EnumValueDefinition
 {
     /**
diff --git a/src/Type/Definition/FieldArgument.php b/src/Type/Definition/FieldArgument.php
index c3e0e6a..8103ab6 100644
--- a/src/Type/Definition/FieldArgument.php
+++ b/src/Type/Definition/FieldArgument.php
@@ -2,8 +2,6 @@
 namespace GraphQL\Type\Definition;
 
 
-use GraphQL\Utils;
-
 /**
  * Class FieldArgument
  *
@@ -17,13 +15,6 @@ class FieldArgument
      */
     public $name;
 
-    /**
-     * @var InputType
-     */
-    private $type;
-
-    private $resolvedType;
-
     /**
      * @var mixed
      */
@@ -34,6 +25,25 @@ class FieldArgument
      */
     public $description;
 
+    /**
+     * @var array
+     */
+    public $config;
+
+    /**
+     * @var InputType|callable
+     */
+    private $type;
+
+    /**
+     * @var InputType
+     */
+    private $resolvedType;
+
+    /**
+     * @param array $config
+     * @return array
+     */
     public static function createMap(array $config)
     {
         $map = [];
@@ -43,13 +53,30 @@ class FieldArgument
         return $map;
     }
 
+    /**
+     * FieldArgument constructor.
+     * @param array $def
+     */
     public function __construct(array $def)
     {
-        foreach ($def as $key => $value) {
-            $this->{$key} = $value;
-        }
+        $def += [
+            'type' => null,
+            'name' => null,
+            'defaultValue' => null,
+            'description' => null
+        ];
+
+        $this->type = $def['type'];
+        $this->name = $def['name'];
+        $this->description = $def['description'];
+        $this->defaultValue = $def['defaultValue'];
+        $this->config = $def;
     }
 
+    /**
+     * @return InputType
+     * @deprecated in favor of setting 'fields' as closure per objectType vs on individual field/argument level
+     */
     public function getType()
     {
         if (null === $this->resolvedType) {
diff --git a/src/Type/Definition/FieldDefinition.php b/src/Type/Definition/FieldDefinition.php
index 928c78a..4d2bc50 100644
--- a/src/Type/Definition/FieldDefinition.php
+++ b/src/Type/Definition/FieldDefinition.php
@@ -1,8 +1,11 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-use GraphQL\Utils;
-
+/**
+ * Class FieldDefinition
+ * @package GraphQL\Type\Definition
+ * @todo Move complexity-related code to it's own place
+ */
 class FieldDefinition
 {
     const DEFAULT_COMPLEXITY_FN = 'GraphQL\Type\Definition\FieldDefinition::defaultComplexity';
@@ -12,16 +15,6 @@ class FieldDefinition
      */
     public $name;
 
-    /**
-     * @var OutputType
-     */
-    private $type;
-
-    /**
-     * @var OutputType
-     */
-    private $resolvedType;
-
     /**
      * @var array<GraphQLFieldArgument>
      */
@@ -60,8 +53,21 @@ class FieldDefinition
      */
     public $config;
 
+    /**
+     * @var OutputType|callable
+     */
+    private $type;
+
+    /**
+     * @var OutputType
+     */
+    private $resolvedType;
+
     private static $def;
 
+    /**
+     * @return array
+     */
     public static function getDefinition()
     {
         return self::$def ?: (self::$def = [
@@ -107,6 +113,10 @@ class FieldDefinition
         return new self($field);
     }
 
+    /**
+     * FieldDefinition constructor.
+     * @param array $config
+     */
     protected function __construct(array $config)
     {
         $this->name = $config['name'];
@@ -139,6 +149,7 @@ class FieldDefinition
     }
 
     /**
+     * @deprecated as of 17.10.2016 in favor of setting 'fields' as closure per ObjectType vs setting on field level
      * @return Type
      */
     public function getType()
@@ -150,6 +161,14 @@ class FieldDefinition
         return $this->resolvedType;
     }
 
+    /**
+     * @return bool
+     */
+    public function isDeprecated()
+    {
+        return !!$this->deprecationReason;
+    }
+
     /**
      * @return callable|\Closure
      */
@@ -158,6 +177,10 @@ class FieldDefinition
         return $this->complexityFn;
     }
 
+    /**
+     * @param $childrenComplexity
+     * @return mixed
+     */
     public static function defaultComplexity($childrenComplexity)
     {
         return $childrenComplexity + 1;
diff --git a/src/Type/Definition/FloatType.php b/src/Type/Definition/FloatType.php
index 85fc027..7beb1df 100644
--- a/src/Type/Definition/FloatType.php
+++ b/src/Type/Definition/FloatType.php
@@ -4,30 +4,56 @@ namespace GraphQL\Type\Definition;
 use GraphQL\Language\AST\FloatValue;
 use GraphQL\Language\AST\IntValue;
 
+/**
+ * Class FloatType
+ * @package GraphQL\Type\Definition
+ */
 class FloatType extends ScalarType
 {
+    /**
+     * @var string
+     */
     public $name = Type::FLOAT;
 
+    /**
+     * @var string
+     */
     public $description =
 'The `Float` scalar type represents signed double-precision fractional
 values as specified by
 [IEEE 754](http://en.wikipedia.org/wiki/IEEE_floating_point). ';
 
+    /**
+     * @param mixed $value
+     * @return float|null
+     */
     public function serialize($value)
     {
         return $this->coerceFloat($value);
     }
 
+    /**
+     * @param mixed $value
+     * @return float|null
+     */
     public function parseValue($value)
     {
         return $this->coerceFloat($value);
     }
 
+    /**
+     * @param $value
+     * @return float|null
+     */
     private function coerceFloat($value)
     {
         return is_numeric($value) || $value === true || $value === false ? (float) $value : null;
     }
 
+    /**
+     * @param $ast
+     * @return float|null
+     */
     public function parseLiteral($ast)
     {
         if ($ast instanceof FloatValue || $ast instanceof IntValue) {
diff --git a/src/Type/Definition/IDType.php b/src/Type/Definition/IDType.php
index 6a18eaa..524d686 100644
--- a/src/Type/Definition/IDType.php
+++ b/src/Type/Definition/IDType.php
@@ -4,10 +4,20 @@ namespace GraphQL\Type\Definition;
 use GraphQL\Language\AST\IntValue;
 use GraphQL\Language\AST\StringValue;
 
+/**
+ * Class IDType
+ * @package GraphQL\Type\Definition
+ */
 class IDType extends ScalarType
 {
+    /**
+     * @var string
+     */
     public $name = 'ID';
 
+    /**
+     * @var string
+     */
     public $description =
 'The `ID` scalar type represents a unique identifier, often used to
 refetch an object or as key for a cache. The ID type appears in a JSON
@@ -15,16 +25,28 @@ response as a String; however, it is not intended to be human-readable.
 When expected as an input type, any string (such as `"4"`) or integer
 (such as `4`) input value will be accepted as an ID.';
 
+    /**
+     * @param mixed $value
+     * @return string
+     */
     public function serialize($value)
     {
         return (string) $value;
     }
 
+    /**
+     * @param mixed $value
+     * @return string
+     */
     public function parseValue($value)
     {
         return (string) $value;
     }
 
+    /**
+     * @param $ast
+     * @return null|string
+     */
     public function parseLiteral($ast)
     {
         if ($ast instanceof StringValue || $ast instanceof IntValue) {
diff --git a/src/Type/Definition/InputObjectField.php b/src/Type/Definition/InputObjectField.php
index cdcf68c..98aa8ed 100644
--- a/src/Type/Definition/InputObjectField.php
+++ b/src/Type/Definition/InputObjectField.php
@@ -1,8 +1,10 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-use GraphQL\Utils;
-
+/**
+ * Class InputObjectField
+ * @package GraphQL\Type\Definition
+ */
 class InputObjectField
 {
     /**
@@ -10,11 +12,6 @@ class InputObjectField
      */
     public $name;
 
-    /**
-     * @var callback|InputType
-     */
-    private $type;
-
     /**
      * @var mixed|null
      */
@@ -25,6 +22,15 @@ class InputObjectField
      */
     public $description;
 
+    /**
+     * @var callback|InputType
+     */
+    public $type;
+
+    /**
+     * InputObjectField constructor.
+     * @param array $opts
+     */
     public function __construct(array $opts)
     {
         foreach ($opts as $k => $v) {
@@ -32,6 +38,10 @@ class InputObjectField
         }
     }
 
+    /**
+     * @deprecated in favor of defining all object 'fields' as closure vs defining closure per field
+     * @return mixed
+     */
     public function getType()
     {
         return Type::resolve($this->type);
diff --git a/src/Type/Definition/InputObjectType.php b/src/Type/Definition/InputObjectType.php
index d5cdb4f..8a6d569 100644
--- a/src/Type/Definition/InputObjectType.php
+++ b/src/Type/Definition/InputObjectType.php
@@ -3,15 +3,26 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Utils;
 
+/**
+ * Class InputObjectType
+ * @package GraphQL\Type\Definition
+ */
 class InputObjectType extends Type implements InputType
 {
     /**
-     * @var array<InputObjectField>
+     * @var InputObjectField[]
      */
-    private $_fields;
+    private $fields;
 
+    /**
+     * @var array
+     */
     public $config;
 
+    /**
+     * InputObjectType constructor.
+     * @param array $config
+     */
     public function __construct(array $config)
     {
         Config::validate($config, [
@@ -35,16 +46,16 @@ class InputObjectType extends Type implements InputType
      */
     public function getFields()
     {
-        if (null === $this->_fields) {
-            $this->_fields = [];
+        if (null === $this->fields) {
+            $this->fields = [];
             $fields = isset($this->config['fields']) ? $this->config['fields'] : [];
             $fields = is_callable($fields) ? call_user_func($fields) : $fields;
             foreach ($fields as $name => $field) {
-                $this->_fields[$name] = new InputObjectField($field + ['name' => $name]);
+                $this->fields[$name] = new InputObjectField($field + ['name' => $name]);
             }
         }
 
-        return $this->_fields;
+        return $this->fields;
     }
 
     /**
@@ -54,10 +65,10 @@ class InputObjectType extends Type implements InputType
      */
     public function getField($name)
     {
-        if (null === $this->_fields) {
+        if (null === $this->fields) {
             $this->getFields();
         }
-        Utils::invariant(isset($this->_fields[$name]), "Field '%s' is not defined for type '%s'", $name, $this->name);
-        return $this->_fields[$name];
+        Utils::invariant(isset($this->fields[$name]), "Field '%s' is not defined for type '%s'", $name, $this->name);
+        return $this->fields[$name];
     }
 }
diff --git a/src/Type/Definition/InputType.php b/src/Type/Definition/InputType.php
index 3bd0031..7f90039 100644
--- a/src/Type/Definition/InputType.php
+++ b/src/Type/Definition/InputType.php
@@ -1,8 +1,6 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-interface InputType
-{
 /*
 export type GraphQLInputType =
   GraphQLScalarType |
@@ -11,4 +9,6 @@ export type GraphQLInputType =
   GraphQLList |
   GraphQLNonNull;
  */
+interface InputType
+{
 }
diff --git a/src/Type/Definition/IntType.php b/src/Type/Definition/IntType.php
index 7b71e96..77a04ed 100644
--- a/src/Type/Definition/IntType.php
+++ b/src/Type/Definition/IntType.php
@@ -4,6 +4,10 @@ namespace GraphQL\Type\Definition;
 use GraphQL\Language\AST\IntValue;
 use GraphQL\Language\AST\Value;
 
+/**
+ * Class IntType
+ * @package GraphQL\Type\Definition
+ */
 class IntType extends ScalarType
 {
     // As per the GraphQL Spec, Integers are only treated as valid when a valid
@@ -14,22 +18,40 @@ class IntType extends ScalarType
     const MAX_INT = 2147483647;
     const MIN_INT = -2147483648;
 
+    /**
+     * @var string
+     */
     public $name = Type::INT;
 
+    /**
+     * @var string
+     */
     public $description =
 'The `Int` scalar type represents non-fractional signed whole numeric
 values. Int can represent values between -(2^31) and 2^31 - 1. ';
 
+    /**
+     * @param mixed $value
+     * @return int|null
+     */
     public function serialize($value)
     {
         return $this->coerceInt($value);
     }
 
+    /**
+     * @param mixed $value
+     * @return int|null
+     */
     public function parseValue($value)
     {
         return $this->coerceInt($value);
     }
 
+    /**
+     * @param $value
+     * @return int|null
+     */
     private function coerceInt($value)
     {
         if (false === $value || true === $value) {
@@ -41,6 +63,10 @@ values. Int can represent values between -(2^31) and 2^31 - 1. ';
         return null;
     }
 
+    /**
+     * @param $ast
+     * @return int|null
+     */
     public function parseLiteral($ast)
     {
         if ($ast instanceof IntValue) {
diff --git a/src/Type/Definition/InterfaceType.php b/src/Type/Definition/InterfaceType.php
index f273a15..b21065f 100644
--- a/src/Type/Definition/InterfaceType.php
+++ b/src/Type/Definition/InterfaceType.php
@@ -1,22 +1,28 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
 use GraphQL\Utils;
 
+/**
+ * Class InterfaceType
+ * @package GraphQL\Type\Definition
+ */
 class InterfaceType extends Type implements AbstractType, OutputType, CompositeType
 {
     /**
      * @var array<string,FieldDefinition>
      */
-    private $_fields;
+    private $fields;
 
+    /**
+     * @var mixed|null
+     */
     public $description;
 
     /**
      * @var callback
      */
-    private $_resolveTypeFn;
+    private $resolveTypeFn;
 
     /**
      * @var array
@@ -41,7 +47,7 @@ class InterfaceType extends Type implements AbstractType, OutputType, CompositeT
 
         $this->name = $config['name'];
         $this->description = isset($config['description']) ? $config['description'] : null;
-        $this->_resolveTypeFn = isset($config['resolveType']) ? $config['resolveType'] : null;
+        $this->resolveTypeFn = isset($config['resolveType']) ? $config['resolveType'] : null;
         $this->config = $config;
     }
 
@@ -50,13 +56,13 @@ class InterfaceType extends Type implements AbstractType, OutputType, CompositeT
      */
     public function getFields()
     {
-        if (null === $this->_fields) {
-            $this->_fields = [];
+        if (null === $this->fields) {
+            $this->fields = [];
             $fields = isset($this->config['fields']) ? $this->config['fields'] : [];
             $fields = is_callable($fields) ? call_user_func($fields) : $fields;
-            $this->_fields = FieldDefinition::createMap($fields);
+            $this->fields = FieldDefinition::createMap($fields);
         }
-        return $this->_fields;
+        return $this->fields;
     }
 
     /**
@@ -66,11 +72,11 @@ class InterfaceType extends Type implements AbstractType, OutputType, CompositeT
      */
     public function getField($name)
     {
-        if (null === $this->_fields) {
+        if (null === $this->fields) {
             $this->getFields();
         }
-        Utils::invariant(isset($this->_fields[$name]), 'Field "%s" is not defined for type "%s"', $name, $this->name);
-        return $this->_fields[$name];
+        Utils::invariant(isset($this->fields[$name]), 'Field "%s" is not defined for type "%s"', $name, $this->name);
+        return $this->fields[$name];
     }
 
     /**
@@ -78,6 +84,6 @@ class InterfaceType extends Type implements AbstractType, OutputType, CompositeT
      */
     public function getResolveTypeFn()
     {
-        return $this->_resolveTypeFn;
+        return $this->resolveTypeFn;
     }
 }
diff --git a/src/Type/Definition/LeafType.php b/src/Type/Definition/LeafType.php
index d037347..a36b592 100644
--- a/src/Type/Definition/LeafType.php
+++ b/src/Type/Definition/LeafType.php
@@ -1,12 +1,11 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
-interface LeafType
-{
 /*
 export type GraphQLLeafType =
 GraphQLScalarType |
 GraphQLEnumType;
 */
+interface LeafType
+{
 }
diff --git a/src/Type/Definition/ListOfType.php b/src/Type/Definition/ListOfType.php
index f1ae5ed..b59ba74 100644
--- a/src/Type/Definition/ListOfType.php
+++ b/src/Type/Definition/ListOfType.php
@@ -1,15 +1,18 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
 use GraphQL\Utils;
 
+/**
+ * Class ListOfType
+ * @package GraphQL\Type\Definition
+ */
 class ListOfType extends Type implements WrappingType, OutputType, InputType
 {
     /**
      * @var callable|Type
      */
-    private $ofType;
+    public $ofType;
 
     /**
      * @param callable|Type $type
diff --git a/src/Type/Definition/NonNull.php b/src/Type/Definition/NonNull.php
index abef493..b4fe61f 100644
--- a/src/Type/Definition/NonNull.php
+++ b/src/Type/Definition/NonNull.php
@@ -4,6 +4,10 @@ namespace GraphQL\Type\Definition;
 use GraphQL\Type\TypeKind;
 use GraphQL\Utils;
 
+/**
+ * Class NonNull
+ * @package GraphQL\Type\Definition
+ */
 class NonNull extends Type implements WrappingType, OutputType, InputType
 {
     /**
diff --git a/src/Type/Definition/ObjectType.php b/src/Type/Definition/ObjectType.php
index 1c04baa..80c43e5 100644
--- a/src/Type/Definition/ObjectType.php
+++ b/src/Type/Definition/ObjectType.php
@@ -11,19 +11,19 @@ use GraphQL\Utils;
  *
  * Example:
  *
- *     var AddressType = new GraphQLObjectType({
- *       name: 'Address',
- *       fields: {
- *         street: { type: GraphQLString },
- *         number: { type: GraphQLInt },
- *         formatted: {
- *           type: GraphQLString,
- *           resolve(obj) {
- *             return obj.number + ' ' + obj.street
+ *     $AddressType = new ObjectType([
+ *       'name' => 'Address',
+ *       'fields' => [
+ *         'street' => [ 'type' => GraphQL\Type\Definition\Type::string() ],
+ *         'number' => [ 'type' => GraphQL\Type\Definition\Type::int() ],
+ *         'formatted' => [
+ *           'type' => GraphQL\Type\Definition\Type::string(),
+ *           'resolve' => function($obj) {
+ *             return $obj->number . ' ' . $obj->street;
  *           }
- *         }
- *       }
- *     });
+ *         ]
+ *       ]
+ *     ]);
  *
  * When two types need to refer to each other, or a type needs to refer to
  * itself in a field, you can use a function expression (aka a closure or a
@@ -31,31 +31,34 @@ use GraphQL\Utils;
  *
  * Example:
  *
- *     var PersonType = new GraphQLObjectType({
- *       name: 'Person',
- *       fields: () => ({
- *         name: { type: GraphQLString },
- *         bestFriend: { type: PersonType },
- *       })
- *     });
+ *     $PersonType = null;
+ *     $PersonType = new ObjectType([
+ *       'name' => 'Person',
+ *       'fields' => function() use (&$PersonType) {
+ *          return [
+ *              'name' => ['type' => GraphQL\Type\Definition\Type::string() ],
+ *              'bestFriend' => [ 'type' => $PersonType ],
+ *          ];
+ *        }
+ *     ]);
  *
  */
 class ObjectType extends Type implements OutputType, CompositeType
 {
     /**
-     * @var array<Field>
+     * @var FieldDefinition[]
      */
-    private $_fields;
+    private $fields;
 
     /**
-     * @var array<InterfaceType>
+     * @var InterfaceType[]
      */
-    private $_interfaces;
+    private $interfaces;
 
     /**
      * @var callable
      */
-    private $_isTypeOf;
+    private $isTypeOf;
 
     /**
      * Keeping reference of config for late bindings and custom app-level metadata
@@ -69,6 +72,10 @@ class ObjectType extends Type implements OutputType, CompositeType
      */
     public $resolveFieldFn;
 
+    /**
+     * ObjectType constructor.
+     * @param array $config
+     */
     public function __construct(array $config)
     {
         Utils::invariant(!empty($config['name']), 'Every type is expected to have name');
@@ -93,7 +100,7 @@ class ObjectType extends Type implements OutputType, CompositeType
         $this->name = $config['name'];
         $this->description = isset($config['description']) ? $config['description'] : null;
         $this->resolveFieldFn = isset($config['resolveField']) ? $config['resolveField'] : null;
-        $this->_isTypeOf = isset($config['isTypeOf']) ? $config['isTypeOf'] : null;
+        $this->isTypeOf = isset($config['isTypeOf']) ? $config['isTypeOf'] : null;
         $this->config = $config;
     }
 
@@ -102,12 +109,12 @@ class ObjectType extends Type implements OutputType, CompositeType
      */
     public function getFields()
     {
-        if (null === $this->_fields) {
+        if (null === $this->fields) {
             $fields = isset($this->config['fields']) ? $this->config['fields'] : [];
             $fields = is_callable($fields) ? call_user_func($fields) : $fields;
-            $this->_fields = FieldDefinition::createMap($fields);
+            $this->fields = FieldDefinition::createMap($fields);
         }
-        return $this->_fields;
+        return $this->fields;
     }
 
     /**
@@ -117,24 +124,24 @@ class ObjectType extends Type implements OutputType, CompositeType
      */
     public function getField($name)
     {
-        if (null === $this->_fields) {
+        if (null === $this->fields) {
             $this->getFields();
         }
-        Utils::invariant(isset($this->_fields[$name]), "Field '%s' is not defined for type '%s'", $name, $this->name);
-        return $this->_fields[$name];
+        Utils::invariant(isset($this->fields[$name]), "Field '%s' is not defined for type '%s'", $name, $this->name);
+        return $this->fields[$name];
     }
 
     /**
-     * @return array<InterfaceType>
+     * @return InterfaceType[]
      */
     public function getInterfaces()
     {
-        if (null === $this->_interfaces) {
+        if (null === $this->interfaces) {
             $interfaces = isset($this->config['interfaces']) ? $this->config['interfaces'] : [];
             $interfaces = is_callable($interfaces) ? call_user_func($interfaces) : $interfaces;
-            $this->_interfaces = $interfaces;
+            $this->interfaces = $interfaces;
         }
-        return $this->_interfaces;
+        return $this->interfaces;
     }
 
     /**
@@ -153,6 +160,6 @@ class ObjectType extends Type implements OutputType, CompositeType
      */
     public function isTypeOf($value, $context, ResolveInfo $info)
     {
-        return isset($this->_isTypeOf) ? call_user_func($this->_isTypeOf, $value, $context, $info) : null;
+        return isset($this->isTypeOf) ? call_user_func($this->isTypeOf, $value, $context, $info) : null;
     }
 }
diff --git a/src/Type/Definition/OutputType.php b/src/Type/Definition/OutputType.php
index c9ee6a0..4765616 100644
--- a/src/Type/Definition/OutputType.php
+++ b/src/Type/Definition/OutputType.php
@@ -2,8 +2,6 @@
 namespace GraphQL\Type\Definition;
 
 
-interface OutputType
-{
 /*
 GraphQLScalarType |
 GraphQLObjectType |
@@ -13,4 +11,6 @@ GraphQLEnumType |
 GraphQLList |
 GraphQLNonNull;
 */
+interface OutputType
+{
 }
diff --git a/src/Type/Definition/ResolveInfo.php b/src/Type/Definition/ResolveInfo.php
index dcdc3ec..e0741c0 100644
--- a/src/Type/Definition/ResolveInfo.php
+++ b/src/Type/Definition/ResolveInfo.php
@@ -10,6 +10,10 @@ use GraphQL\Language\AST\SelectionSet;
 use GraphQL\Schema;
 use GraphQL\Utils;
 
+/**
+ * Class ResolveInfo
+ * @package GraphQL\Type\Definition
+ */
 class ResolveInfo
 {
     /**
diff --git a/src/Type/Definition/ScalarType.php b/src/Type/Definition/ScalarType.php
index cc840ca..e327910 100644
--- a/src/Type/Definition/ScalarType.php
+++ b/src/Type/Definition/ScalarType.php
@@ -12,24 +12,46 @@ use GraphQL\Utils;
  *
  * Example:
  *
- *     var OddType = new GraphQLScalarType({
- *       name: 'Odd',
- *       serialize(value) {
- *         return value % 2 === 1 ? value : null;
- *       }
- *     });
- *
+ * class OddType extends ScalarType
+ * {
+ *     public $name = 'Odd',
+ *     public function serialize($value)
+ *     {
+ *         return $value % 2 === 1 ? $value : null;
+ *     }
+ * }
  */
-abstract class ScalarType extends Type implements OutputType, InputType
+abstract class ScalarType extends Type implements OutputType, InputType, LeafType
 {
+    /**
+     * ScalarType constructor.
+     */
     protected function __construct()
     {
         Utils::invariant($this->name, 'Type must be named.');
     }
 
+    /**
+     * Serializes an internal value to include in a response.
+     *
+     * @param mixed $value
+     * @return mixed
+     */
     abstract public function serialize($value);
 
+    /**
+     * Parses an externally provided value to use as an input
+     *
+     * @param mixed $value
+     * @return mixed
+     */
     abstract public function parseValue($value);
 
+    /**
+     * Parses an externally provided literal value to use as an input
+     *
+     * @param $valueAST
+     * @return mixed
+     */
     abstract public function parseLiteral(/* GraphQL\Language\AST\Value */$valueAST);
 }
diff --git a/src/Type/Definition/StringType.php b/src/Type/Definition/StringType.php
index 927cfba..13ca111 100644
--- a/src/Type/Definition/StringType.php
+++ b/src/Type/Definition/StringType.php
@@ -3,20 +3,38 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Language\AST\StringValue;
 
+/**
+ * Class StringType
+ * @package GraphQL\Type\Definition
+ */
 class StringType extends ScalarType
 {
+    /**
+     * @var string
+     */
     public $name = Type::STRING;
 
+    /**
+     * @var string
+     */
     public $description =
 'The `String` scalar type represents textual data, represented as UTF-8
 character sequences. The String type is most often used by GraphQL to
 represent free-form human-readable text.';
 
+    /**
+     * @param mixed $value
+     * @return mixed|string
+     */
     public function serialize($value)
     {
         return $this->parseValue($value);
     }
 
+    /**
+     * @param mixed $value
+     * @return string
+     */
     public function parseValue($value)
     {
         if ($value === true) {
@@ -28,6 +46,10 @@ represent free-form human-readable text.';
         return (string) $value;
     }
 
+    /**
+     * @param $ast
+     * @return null|string
+     */
     public function parseLiteral($ast)
     {
         if ($ast instanceof StringValue) {
diff --git a/src/Type/Definition/Type.php b/src/Type/Definition/Type.php
index 8e92f42..b483d7f 100644
--- a/src/Type/Definition/Type.php
+++ b/src/Type/Definition/Type.php
@@ -3,8 +3,6 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Utils;
 
-abstract class Type
-{
 /*
 export type GraphQLType =
 GraphQLScalarType |
@@ -16,14 +14,22 @@ GraphQLInputObjectType |
 GraphQLList |
 GraphQLNonNull;
 */
+abstract class Type
+{
     const STRING = 'String';
     const INT = 'Int';
     const BOOLEAN = 'Boolean';
     const FLOAT = 'Float';
     const ID = 'ID';
 
+    /**
+     * @var array
+     */
     private static $internalTypes;
 
+    /**
+     * @return IDType
+     */
     public static function id()
     {
         return self::getInternalType(self::ID);
@@ -81,7 +87,7 @@ GraphQLNonNull;
 
     /**
      * @param $name
-     * @return Type
+     * @return Type|array
      */
     private static function getInternalType($name = null)
     {
@@ -125,21 +131,29 @@ GraphQLNonNull;
         return $nakedType instanceof OutputType;
     }
 
+    /**
+     * @param $type
+     * @return bool
+     */
     public static function isLeafType($type)
     {
-        // TODO: add LeafType interface
         $nakedType = self::getNamedType($type);
-        return (
-            $nakedType instanceof ScalarType ||
-            $nakedType instanceof EnumType
-        );
+        return $nakedType instanceof LeafType;
     }
 
+    /**
+     * @param $type
+     * @return bool
+     */
     public static function isCompositeType($type)
     {
         return $type instanceof CompositeType;
     }
 
+    /**
+     * @param $type
+     * @return bool
+     */
     public static function isAbstractType($type)
     {
         return $type instanceof AbstractType;
@@ -169,6 +183,11 @@ GraphQLNonNull;
         return self::resolve($type);
     }
 
+    /**
+     * @param $type
+     * @deprecated in favor of defining ObjectType 'fields' as closure (vs defining closure per field type)
+     * @return mixed
+     */
     public static function resolve($type)
     {
         if (is_callable($type)) {
@@ -213,11 +232,17 @@ GraphQLNonNull;
      */
     public $description;
 
+    /**
+     * @return string
+     */
     public function toString()
     {
         return $this->name;
     }
 
+    /**
+     * @return string
+     */
     public function __toString()
     {
         try {
diff --git a/src/Type/Definition/UnionType.php b/src/Type/Definition/UnionType.php
index 39e2caa..5fe0966 100644
--- a/src/Type/Definition/UnionType.php
+++ b/src/Type/Definition/UnionType.php
@@ -3,28 +3,36 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Utils;
 
+/**
+ * Class UnionType
+ * @package GraphQL\Type\Definition
+ */
 class UnionType extends Type implements AbstractType, OutputType, CompositeType
 {
     /**
      * @var ObjectType[]
      */
-    private $_types;
+    private $types;
 
     /**
      * @var array<string, ObjectType>
      */
-    private $_possibleTypeNames;
+    private $possibleTypeNames;
 
     /**
      * @var callback
      */
-    private $_resolveTypeFn;
+    private $resolveTypeFn;
 
     /**
      * @var array
      */
-    private $_config;
+    public $config;
 
+    /**
+     * UnionType constructor.
+     * @param $config
+     */
     public function __construct($config)
     {
         Config::validate($config, [
@@ -43,11 +51,14 @@ class UnionType extends Type implements AbstractType, OutputType, CompositeType
          */
         $this->name = $config['name'];
         $this->description = isset($config['description']) ? $config['description'] : null;
-        $this->_types = $config['types'];
-        $this->_resolveTypeFn = isset($config['resolveType']) ? $config['resolveType'] : null;
-        $this->_config = $config;
+        $this->types = $config['types'];
+        $this->resolveTypeFn = isset($config['resolveType']) ? $config['resolveType'] : null;
+        $this->config = $config;
     }
 
+    /**
+     * @return ObjectType[]
+     */
     public function getPossibleTypes()
     {
         trigger_error(__METHOD__ . ' is deprecated in favor of ' . __CLASS__ . '::getTypes()', E_USER_DEPRECATED);
@@ -59,10 +70,10 @@ class UnionType extends Type implements AbstractType, OutputType, CompositeType
      */
     public function getTypes()
     {
-        if ($this->_types instanceof \Closure) {
-            $this->_types = call_user_func($this->_types);
+        if ($this->types instanceof \Closure) {
+            $this->types = call_user_func($this->types);
         }
-        return $this->_types;
+        return $this->types;
     }
 
     /**
@@ -75,13 +86,13 @@ class UnionType extends Type implements AbstractType, OutputType, CompositeType
             return false;
         }
 
-        if (null === $this->_possibleTypeNames) {
-            $this->_possibleTypeNames = [];
+        if (null === $this->possibleTypeNames) {
+            $this->possibleTypeNames = [];
             foreach ($this->getTypes() as $possibleType) {
-                $this->_possibleTypeNames[$possibleType->name] = true;
+                $this->possibleTypeNames[$possibleType->name] = true;
             }
         }
-        return isset($this->_possibleTypeNames[$type->name]);
+        return isset($this->possibleTypeNames[$type->name]);
     }
 
     /**
@@ -89,6 +100,6 @@ class UnionType extends Type implements AbstractType, OutputType, CompositeType
      */
     public function getResolveTypeFn()
     {
-        return $this->_resolveTypeFn;
+        return $this->resolveTypeFn;
     }
 }
diff --git a/src/Type/Definition/UnmodifiedType.php b/src/Type/Definition/UnmodifiedType.php
index b13d9b2..ef01c10 100644
--- a/src/Type/Definition/UnmodifiedType.php
+++ b/src/Type/Definition/UnmodifiedType.php
@@ -1,9 +1,6 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
-interface UnmodifiedType
-{
 /*
 export type GraphQLUnmodifiedType =
 GraphQLScalarType |
@@ -13,4 +10,6 @@ GraphQLUnionType |
 GraphQLEnumType |
 GraphQLInputObjectType;
 */
+interface UnmodifiedType
+{
 }
diff --git a/src/Type/Definition/WrappingType.php b/src/Type/Definition/WrappingType.php
index 1f275bc..f2469ce 100644
--- a/src/Type/Definition/WrappingType.php
+++ b/src/Type/Definition/WrappingType.php
@@ -1,12 +1,15 @@
 <?php
 namespace GraphQL\Type\Definition;
 
-
-interface WrappingType
-{
 /*
 NonNullType
 ListOfType
  */
+interface WrappingType
+{
+    /**
+     * @param bool $recurse
+     * @return Type
+     */
     public function getWrappedType($recurse = false);
 }
diff --git a/src/Type/Introspection.php b/src/Type/Introspection.php
index 93a71c4..c8e2ffa 100644
--- a/src/Type/Introspection.php
+++ b/src/Type/Introspection.php
@@ -32,7 +32,7 @@ class TypeKind {
 
 class Introspection
 {
-    private static $_map = [];
+    private static $map = [];
 
     /**
      * @return string
@@ -198,8 +198,8 @@ EOD;
 
     public static function _schema()
     {
-        if (!isset(self::$_map['__Schema'])) {
-            self::$_map['__Schema'] = new ObjectType([
+        if (!isset(self::$map['__Schema'])) {
+            self::$map['__Schema'] = new ObjectType([
                 'name' => '__Schema',
                 'description' =>
                     'A GraphQL Schema defines the capabilities of a GraphQL ' .
@@ -247,13 +247,13 @@ EOD;
                 ]
             ]);
         }
-        return self::$_map['__Schema'];
+        return self::$map['__Schema'];
     }
 
     public static function _directive()
     {
-        if (!isset(self::$_map['__Directive'])) {
-            self::$_map['__Directive'] = new ObjectType([
+        if (!isset(self::$map['__Directive'])) {
+            self::$map['__Directive'] = new ObjectType([
                 'name' => '__Directive',
                 'description' =>     'A Directive provides a way to describe alternate runtime execution and ' .
                     'type validation behavior in a GraphQL document.' .
@@ -306,13 +306,13 @@ EOD;
                 ]
             ]);
         }
-        return self::$_map['__Directive'];
+        return self::$map['__Directive'];
     }
 
     public static function _directiveLocation()
     {
-        if (!isset(self::$_map['__DirectiveLocation'])) {
-            self::$_map['__DirectiveLocation'] = new EnumType([
+        if (!isset(self::$map['__DirectiveLocation'])) {
+            self::$map['__DirectiveLocation'] = new EnumType([
                 'name' => '__DirectiveLocation',
                 'description' =>
                     'A Directive can be adjacent to many parts of the GraphQL language, a ' .
@@ -349,13 +349,13 @@ EOD;
                 ]
             ]);
         }
-        return self::$_map['__DirectiveLocation'];
+        return self::$map['__DirectiveLocation'];
     }
 
     public static function _type()
     {
-        if (!isset(self::$_map['__Type'])) {
-            self::$_map['__Type'] = new ObjectType([
+        if (!isset(self::$map['__Type'])) {
+            self::$map['__Type'] = new ObjectType([
                 'name' => '__Type',
                 'description' =>
                     'The fundamental unit of any GraphQL Schema is the type. There are ' .
@@ -474,14 +474,14 @@ EOD;
                 }
             ]);
         }
-        return self::$_map['__Type'];
+        return self::$map['__Type'];
     }
 
     public static function _field()
     {
-        if (!isset(self::$_map['__Field'])) {
+        if (!isset(self::$map['__Field'])) {
 
-            self::$_map['__Field'] = new ObjectType([
+            self::$map['__Field'] = new ObjectType([
                 'name' => '__Field',
                 'description' =>
                     'Object and Interface types are described by a list of Fields, each of ' .
@@ -515,13 +515,13 @@ EOD;
                 }
             ]);
         }
-        return self::$_map['__Field'];
+        return self::$map['__Field'];
     }
 
     public static function _inputValue()
     {
-        if (!isset(self::$_map['__InputValue'])) {
-            self::$_map['__InputValue'] = new ObjectType([
+        if (!isset(self::$map['__InputValue'])) {
+            self::$map['__InputValue'] = new ObjectType([
                 'name' => '__InputValue',
                 'description' =>
                     'Arguments provided to Fields or Directives and the input fields of an ' .
@@ -549,13 +549,13 @@ EOD;
                 }
             ]);
         }
-        return self::$_map['__InputValue'];
+        return self::$map['__InputValue'];
     }
 
     public static function _enumValue()
     {
-        if (!isset(self::$_map['__EnumValue'])) {
-            self::$_map['__EnumValue'] = new ObjectType([
+        if (!isset(self::$map['__EnumValue'])) {
+            self::$map['__EnumValue'] = new ObjectType([
                 'name' => '__EnumValue',
                 'description' =>
                     'One possible value for a given Enum. Enum values are unique values, not ' .
@@ -576,13 +576,13 @@ EOD;
                 ]
             ]);
         }
-        return self::$_map['__EnumValue'];
+        return self::$map['__EnumValue'];
     }
 
     public static function _typeKind()
     {
-        if (!isset(self::$_map['__TypeKind'])) {
-            self::$_map['__TypeKind'] = new EnumType([
+        if (!isset(self::$map['__TypeKind'])) {
+            self::$map['__TypeKind'] = new EnumType([
                 'name' => '__TypeKind',
                 'description' => 'An enum describing what kind of type a given __Type is.',
                 'values' => [
@@ -621,13 +621,13 @@ EOD;
                 ]
             ]);
         }
-        return self::$_map['__TypeKind'];
+        return self::$map['__TypeKind'];
     }
 
     public static function schemaMetaFieldDef()
     {
-        if (!isset(self::$_map['__schema'])) {
-            self::$_map['__schema'] = FieldDefinition::create([
+        if (!isset(self::$map['__schema'])) {
+            self::$map['__schema'] = FieldDefinition::create([
                 'name' => '__schema',
                 'type' => Type::nonNull(self::_schema()),
                 'description' => 'Access the current type schema of this server.',
@@ -642,13 +642,13 @@ EOD;
                 }
             ]);
         }
-        return self::$_map['__schema'];
+        return self::$map['__schema'];
     }
 
     public static function typeMetaFieldDef()
     {
-        if (!isset(self::$_map['__type'])) {
-            self::$_map['__type'] = FieldDefinition::create([
+        if (!isset(self::$map['__type'])) {
+            self::$map['__type'] = FieldDefinition::create([
                 'name' => '__type',
                 'type' => self::_type(),
                 'description' => 'Request the type information of a single type.',
@@ -660,13 +660,13 @@ EOD;
                 }
             ]);
         }
-        return self::$_map['__type'];
+        return self::$map['__type'];
     }
 
     public static function typeNameMetaFieldDef()
     {
-        if (!isset(self::$_map['__typename'])) {
-            self::$_map['__typename'] = FieldDefinition::create([
+        if (!isset(self::$map['__typename'])) {
+            self::$map['__typename'] = FieldDefinition::create([
                 'name' => '__typename',
                 'type' => Type::nonNull(Type::string()),
                 'description' => 'The name of the current Object type at runtime.',
@@ -681,6 +681,6 @@ EOD;
                 }
             ]);
         }
-        return self::$_map['__typename'];
+        return self::$map['__typename'];
     }
 }
diff --git a/src/Utils/AST.php b/src/Utils/AST.php
index b58a14c..88ea3aa 100644
--- a/src/Utils/AST.php
+++ b/src/Utils/AST.php
@@ -22,6 +22,10 @@ use GraphQL\Type\Definition\ScalarType;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Utils;
 
+/**
+ * Class AST
+ * @package GraphQL\Utils
+ */
 class AST
 {
     /**
diff --git a/src/Utils/PairSet.php b/src/Utils/PairSet.php
index 3d89561..367b7b0 100644
--- a/src/Utils/PairSet.php
+++ b/src/Utils/PairSet.php
@@ -1,60 +1,86 @@
 <?php
 namespace GraphQL\Utils;
 
-
+/**
+ * Class PairSet
+ * @package GraphQL\Utils
+ */
 class PairSet
 {
     /**
      * @var \SplObjectStorage<any, Set<any>>
      */
-    private $_data;
+    private $data;
 
-    private $_wrappers = [];
+    /**
+     * @var array
+     */
+    private $wrappers = [];
 
+    /**
+     * PairSet constructor.
+     */
     public function __construct()
     {
-        $this->_data = new \SplObjectStorage(); // SplObject hash instead?
+        $this->data = new \SplObjectStorage(); // SplObject hash instead?
     }
 
+    /**
+     * @param $a
+     * @param $b
+     * @return null|object
+     */
     public function has($a, $b)
     {
-        $a = $this->_toObj($a);
-        $b = $this->_toObj($b);
+        $a = $this->toObj($a);
+        $b = $this->toObj($b);
 
         /** @var \SplObjectStorage $first */
-        $first = isset($this->_data[$a]) ? $this->_data[$a] : null;
+        $first = isset($this->data[$a]) ? $this->data[$a] : null;
         return isset($first, $first[$b]) ? $first[$b] : null;
     }
 
+    /**
+     * @param $a
+     * @param $b
+     */
     public function add($a, $b)
     {
-        $this->_pairSetAdd($a, $b);
-        $this->_pairSetAdd($b, $a);
+        $this->pairSetAdd($a, $b);
+        $this->pairSetAdd($b, $a);
     }
 
-    private function _toObj($var)
+    /**
+     * @param $var
+     * @return mixed
+     */
+    private function toObj($var)
     {
         // SplObjectStorage expects objects, so wrapping non-objects to objects
         if (is_object($var)) {
             return $var;
         }
-        if (!isset($this->_wrappers[$var])) {
+        if (!isset($this->wrappers[$var])) {
             $tmp = new \stdClass();
             $tmp->_internal = $var;
-            $this->_wrappers[$var] = $tmp;
+            $this->wrappers[$var] = $tmp;
         }
-        return $this->_wrappers[$var];
+        return $this->wrappers[$var];
     }
 
-    private function _pairSetAdd($a, $b)
+    /**
+     * @param $a
+     * @param $b
+     */
+    private function pairSetAdd($a, $b)
     {
-        $a = $this->_toObj($a);
-        $b = $this->_toObj($b);
-        $set = isset($this->_data[$a]) ? $this->_data[$a] : null;
+        $a = $this->toObj($a);
+        $b = $this->toObj($b);
+        $set = isset($this->data[$a]) ? $this->data[$a] : null;
 
         if (!isset($set)) {
             $set = new \SplObjectStorage();
-            $this->_data[$a] = $set;
+            $this->data[$a] = $set;
         }
         $set[$b] = true;
     }
diff --git a/src/Utils/TypeInfo.php b/src/Utils/TypeInfo.php
index 9c85704..740b1e6 100644
--- a/src/Utils/TypeInfo.php
+++ b/src/Utils/TypeInfo.php
@@ -23,6 +23,10 @@ use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Introspection;
 use GraphQL\Utils;
 
+/**
+ * Class TypeInfo
+ * @package GraphQL\Utils
+ */
 class TypeInfo
 {
     /**
@@ -163,7 +167,7 @@ class TypeInfo
      *
      * @return FieldDefinition
      */
-    static private function _getFieldDef(Schema $schema, Type $parentType, Field $fieldAST)
+    static private function getFieldDefinition(Schema $schema, Type $parentType, Field $fieldAST)
     {
         $name = $fieldAST->name->value;
         $schemaMeta = Introspection::schemaMetaFieldDef();
@@ -195,45 +199,49 @@ class TypeInfo
     /**
      * @var Schema
      */
-    private $_schema;
+    private $schema;
 
     /**
      * @var \SplStack<OutputType>
      */
-    private $_typeStack;
+    private $typeStack;
 
     /**
      * @var \SplStack<CompositeType>
      */
-    private $_parentTypeStack;
+    private $parentTypeStack;
 
     /**
      * @var \SplStack<InputType>
      */
-    private $_inputTypeStack;
+    private $inputTypeStack;
 
     /**
      * @var \SplStack<FieldDefinition>
      */
-    private $_fieldDefStack;
+    private $fieldDefStack;
 
     /**
      * @var Directive
      */
-    private $_directive;
+    private $directive;
 
     /**
      * @var FieldArgument
      */
-    private $_argument;
+    private $argument;
 
+    /**
+     * TypeInfo constructor.
+     * @param Schema $schema
+     */
     public function __construct(Schema $schema)
     {
-        $this->_schema = $schema;
-        $this->_typeStack = [];
-        $this->_parentTypeStack = [];
-        $this->_inputTypeStack = [];
-        $this->_fieldDefStack = [];
+        $this->schema = $schema;
+        $this->typeStack = [];
+        $this->parentTypeStack = [];
+        $this->inputTypeStack = [];
+        $this->fieldDefStack = [];
     }
 
     /**
@@ -241,8 +249,8 @@ class TypeInfo
      */
     function getType()
     {
-        if (!empty($this->_typeStack)) {
-            return $this->_typeStack[count($this->_typeStack) - 1];
+        if (!empty($this->typeStack)) {
+            return $this->typeStack[count($this->typeStack) - 1];
         }
         return null;
     }
@@ -252,8 +260,8 @@ class TypeInfo
      */
     function getParentType()
     {
-        if (!empty($this->_parentTypeStack)) {
-            return $this->_parentTypeStack[count($this->_parentTypeStack) - 1];
+        if (!empty($this->parentTypeStack)) {
+            return $this->parentTypeStack[count($this->parentTypeStack) - 1];
         }
         return null;
     }
@@ -263,8 +271,8 @@ class TypeInfo
      */
     function getInputType()
     {
-        if (!empty($this->_inputTypeStack)) {
-            return $this->_inputTypeStack[count($this->_inputTypeStack) - 1];
+        if (!empty($this->inputTypeStack)) {
+            return $this->inputTypeStack[count($this->inputTypeStack) - 1];
         }
         return null;
     }
@@ -274,8 +282,8 @@ class TypeInfo
      */
     function getFieldDef()
     {
-        if (!empty($this->_fieldDefStack)) {
-            return $this->_fieldDefStack[count($this->_fieldDefStack) - 1];
+        if (!empty($this->fieldDefStack)) {
+            return $this->fieldDefStack[count($this->fieldDefStack) - 1];
         }
         return null;
     }
@@ -285,7 +293,7 @@ class TypeInfo
      */
     function getDirective()
     {
-        return $this->_directive;
+        return $this->directive;
     }
 
     /**
@@ -293,12 +301,15 @@ class TypeInfo
      */
     function getArgument()
     {
-        return $this->_argument;
+        return $this->argument;
     }
 
+    /**
+     * @param Node $node
+     */
     function enter(Node $node)
     {
-        $schema = $this->_schema;
+        $schema = $this->schema;
 
         switch ($node->kind) {
             case Node::SELECTION_SET:
@@ -308,21 +319,21 @@ class TypeInfo
                     // isCompositeType is a type refining predicate, so this is safe.
                     $compositeType = $namedType;
                 }
-                $this->_parentTypeStack[] = $compositeType; // push
+                $this->parentTypeStack[] = $compositeType; // push
                 break;
 
             case Node::FIELD:
                 $parentType = $this->getParentType();
                 $fieldDef = null;
                 if ($parentType) {
-                    $fieldDef = self::_getFieldDef($schema, $parentType, $node);
+                    $fieldDef = self::getFieldDefinition($schema, $parentType, $node);
                 }
-                $this->_fieldDefStack[] = $fieldDef; // push
-                $this->_typeStack[] = $fieldDef ? $fieldDef->getType() : null; // push
+                $this->fieldDefStack[] = $fieldDef; // push
+                $this->typeStack[] = $fieldDef ? $fieldDef->getType() : null; // push
                 break;
 
             case Node::DIRECTIVE:
-                $this->_directive = $schema->getDirective($node->name->value);
+                $this->directive = $schema->getDirective($node->name->value);
                 break;
 
             case Node::OPERATION_DEFINITION:
@@ -334,19 +345,19 @@ class TypeInfo
                 } else if ($node->operation === 'subscription') {
                     $type = $schema->getSubscriptionType();
                 }
-                $this->_typeStack[] = $type; // push
+                $this->typeStack[] = $type; // push
                 break;
 
             case Node::INLINE_FRAGMENT:
             case Node::FRAGMENT_DEFINITION:
                 $typeConditionAST = $node->typeCondition;
                 $outputType = $typeConditionAST ? self::typeFromAST($schema, $typeConditionAST) : $this->getType();
-                $this->_typeStack[] = $outputType; // push
+                $this->typeStack[] = $outputType; // push
                 break;
 
             case Node::VARIABLE_DEFINITION:
                 $inputType = self::typeFromAST($schema, $node->type);
-                $this->_inputTypeStack[] = $inputType; // push
+                $this->inputTypeStack[] = $inputType; // push
                 break;
 
             case Node::ARGUMENT:
@@ -358,13 +369,13 @@ class TypeInfo
                         $argType = $argDef->getType();
                     }
                 }
-                $this->_argument = $argDef;
-                $this->_inputTypeStack[] = $argType; // push
+                $this->argument = $argDef;
+                $this->inputTypeStack[] = $argType; // push
                 break;
 
             case Node::LST:
                 $listType = Type::getNullableType($this->getInputType());
-                $this->_inputTypeStack[] = ($listType instanceof ListOfType ? $listType->getWrappedType() : null); // push
+                $this->inputTypeStack[] = ($listType instanceof ListOfType ? $listType->getWrappedType() : null); // push
                 break;
 
             case Node::OBJECT_FIELD:
@@ -375,42 +386,45 @@ class TypeInfo
                     $inputField = isset($tmp[$node->name->value]) ? $tmp[$node->name->value] : null;
                     $fieldType = $inputField ? $inputField->getType() : null;
                 }
-                $this->_inputTypeStack[] = $fieldType;
+                $this->inputTypeStack[] = $fieldType;
             break;
         }
     }
 
+    /**
+     * @param Node $node
+     */
     function leave(Node $node)
     {
         switch ($node->kind) {
             case Node::SELECTION_SET:
-                array_pop($this->_parentTypeStack);
+                array_pop($this->parentTypeStack);
                 break;
 
             case Node::FIELD:
-                array_pop($this->_fieldDefStack);
-                array_pop($this->_typeStack);
+                array_pop($this->fieldDefStack);
+                array_pop($this->typeStack);
                 break;
 
             case Node::DIRECTIVE:
-                $this->_directive = null;
+                $this->directive = null;
                 break;
 
             case Node::OPERATION_DEFINITION:
             case Node::INLINE_FRAGMENT:
             case Node::FRAGMENT_DEFINITION:
-                array_pop($this->_typeStack);
+                array_pop($this->typeStack);
                 break;
             case Node::VARIABLE_DEFINITION:
-                array_pop($this->_inputTypeStack);
+                array_pop($this->inputTypeStack);
                 break;
             case Node::ARGUMENT:
-                $this->_argument = null;
-                array_pop($this->_inputTypeStack);
+                $this->argument = null;
+                array_pop($this->inputTypeStack);
                 break;
             case Node::LST:
             case Node::OBJECT_FIELD:
-                array_pop($this->_inputTypeStack);
+                array_pop($this->inputTypeStack);
                 break;
         }
     }
diff --git a/src/Validator/Rules/AbstractQuerySecurity.php b/src/Validator/Rules/AbstractQuerySecurity.php
index a35c046..7c61e58 100644
--- a/src/Validator/Rules/AbstractQuerySecurity.php
+++ b/src/Validator/Rules/AbstractQuerySecurity.php
@@ -17,7 +17,9 @@ abstract class AbstractQuerySecurity
 {
     const DISABLED = 0;
 
-    /** @var FragmentDefinition[] */
+    /**
+     * @var FragmentDefinition[]
+     */
     private $fragments = [];
 
     /**
diff --git a/src/Validator/ValidationContext.php b/src/Validator/ValidationContext.php
index ed2b4b0..b8f6312 100644
--- a/src/Validator/ValidationContext.php
+++ b/src/Validator/ValidationContext.php
@@ -29,47 +29,47 @@ class ValidationContext
     /**
      * @var Schema
      */
-    private $_schema;
+    private $schema;
 
     /**
      * @var Document
      */
-    private $_ast;
+    private $ast;
 
     /**
      * @var TypeInfo
      */
-    private $_typeInfo;
+    private $typeInfo;
 
     /**
      * @var Error[]
      */
-    private $_errors;
+    private $errors;
 
     /**
      * @var array<string, FragmentDefinition>
      */
-    private $_fragments;
+    private $fragments;
 
     /**
      * @var SplObjectStorage
      */
-    private $_fragmentSpreads;
+    private $fragmentSpreads;
 
     /**
      * @var SplObjectStorage
      */
-    private $_recursivelyReferencedFragments;
+    private $recursivelyReferencedFragments;
 
     /**
      * @var SplObjectStorage
      */
-    private $_variableUsages;
+    private $variableUsages;
 
     /**
      * @var SplObjectStorage
      */
-    private $_recursiveVariableUsages;
+    private $recursiveVariableUsages;
 
     /**
      * ValidationContext constructor.
@@ -80,14 +80,14 @@ class ValidationContext
      */
     function __construct(Schema $schema, Document $ast, TypeInfo $typeInfo)
     {
-        $this->_schema = $schema;
-        $this->_ast = $ast;
-        $this->_typeInfo = $typeInfo;
-        $this->_errors = [];
-        $this->_fragmentSpreads = new SplObjectStorage();
-        $this->_recursivelyReferencedFragments = new SplObjectStorage();
-        $this->_variableUsages = new SplObjectStorage();
-        $this->_recursiveVariableUsages = new SplObjectStorage();
+        $this->schema = $schema;
+        $this->ast = $ast;
+        $this->typeInfo = $typeInfo;
+        $this->errors = [];
+        $this->fragmentSpreads = new SplObjectStorage();
+        $this->recursivelyReferencedFragments = new SplObjectStorage();
+        $this->variableUsages = new SplObjectStorage();
+        $this->recursiveVariableUsages = new SplObjectStorage();
     }
 
     /**
@@ -95,7 +95,7 @@ class ValidationContext
      */
     function reportError(Error $error)
     {
-        $this->_errors[] = $error;
+        $this->errors[] = $error;
     }
 
     /**
@@ -103,7 +103,7 @@ class ValidationContext
      */
     function getErrors()
     {
-        return $this->_errors;
+        return $this->errors;
     }
 
     /**
@@ -111,7 +111,7 @@ class ValidationContext
      */
     function getSchema()
     {
-        return $this->_schema;
+        return $this->schema;
     }
 
     /**
@@ -119,7 +119,7 @@ class ValidationContext
      */
     function getDocument()
     {
-        return $this->_ast;
+        return $this->ast;
     }
 
     /**
@@ -128,9 +128,9 @@ class ValidationContext
      */
     function getFragment($name)
     {
-        $fragments = $this->_fragments;
+        $fragments = $this->fragments;
         if (!$fragments) {
-            $this->_fragments = $fragments =
+            $this->fragments = $fragments =
                 array_reduce($this->getDocument()->definitions, function($frags, $statement) {
                     if ($statement->kind === Node::FRAGMENT_DEFINITION) {
                         $frags[$statement->name->value] = $statement;
@@ -147,7 +147,7 @@ class ValidationContext
      */
     function getFragmentSpreads(HasSelectionSet $node)
     {
-        $spreads = isset($this->_fragmentSpreads[$node]) ? $this->_fragmentSpreads[$node] : null;
+        $spreads = isset($this->fragmentSpreads[$node]) ? $this->fragmentSpreads[$node] : null;
         if (!$spreads) {
             $spreads = [];
             $setsToVisit = [$node->selectionSet];
@@ -163,7 +163,7 @@ class ValidationContext
                     }
                 }
             }
-            $this->_fragmentSpreads[$node] = $spreads;
+            $this->fragmentSpreads[$node] = $spreads;
         }
         return $spreads;
     }
@@ -174,7 +174,7 @@ class ValidationContext
      */
     function getRecursivelyReferencedFragments(OperationDefinition $operation)
     {
-        $fragments = isset($this->_recursivelyReferencedFragments[$operation]) ? $this->_recursivelyReferencedFragments[$operation] : null;
+        $fragments = isset($this->recursivelyReferencedFragments[$operation]) ? $this->recursivelyReferencedFragments[$operation] : null;
 
         if (!$fragments) {
             $fragments = [];
@@ -196,7 +196,7 @@ class ValidationContext
                     }
                 }
             }
-            $this->_recursivelyReferencedFragments[$operation] = $fragments;
+            $this->recursivelyReferencedFragments[$operation] = $fragments;
         }
         return $fragments;
     }
@@ -207,11 +207,11 @@ class ValidationContext
      */
     function getVariableUsages(HasSelectionSet $node)
     {
-        $usages = isset($this->_variableUsages[$node]) ? $this->_variableUsages[$node] : null;
+        $usages = isset($this->variableUsages[$node]) ? $this->variableUsages[$node] : null;
 
         if (!$usages) {
             $newUsages = [];
-            $typeInfo = new TypeInfo($this->_schema);
+            $typeInfo = new TypeInfo($this->schema);
             Visitor::visit($node, Visitor::visitWithTypeInfo($typeInfo, [
                 Node::VARIABLE_DEFINITION => function () {
                     return false;
@@ -221,7 +221,7 @@ class ValidationContext
                 }
             ]));
             $usages = $newUsages;
-            $this->_variableUsages[$node] = $usages;
+            $this->variableUsages[$node] = $usages;
         }
         return $usages;
     }
@@ -232,7 +232,7 @@ class ValidationContext
      */
     function getRecursiveVariableUsages(OperationDefinition $operation)
     {
-        $usages = isset($this->_recursiveVariableUsages[$operation]) ? $this->_recursiveVariableUsages[$operation] : null;
+        $usages = isset($this->recursiveVariableUsages[$operation]) ? $this->recursiveVariableUsages[$operation] : null;
 
         if (!$usages) {
             $usages = $this->getVariableUsages($operation);
@@ -243,7 +243,7 @@ class ValidationContext
                 $tmp[] = $this->getVariableUsages($fragments[$i]);
             }
             $usages = call_user_func_array('array_merge', $tmp);
-            $this->_recursiveVariableUsages[$operation] = $usages;
+            $this->recursiveVariableUsages[$operation] = $usages;
         }
         return $usages;
     }
@@ -255,7 +255,7 @@ class ValidationContext
      */
     function getType()
     {
-        return $this->_typeInfo->getType();
+        return $this->typeInfo->getType();
     }
 
     /**
@@ -263,7 +263,7 @@ class ValidationContext
      */
     function getParentType()
     {
-        return $this->_typeInfo->getParentType();
+        return $this->typeInfo->getParentType();
     }
 
     /**
@@ -271,7 +271,7 @@ class ValidationContext
      */
     function getInputType()
     {
-        return $this->_typeInfo->getInputType();
+        return $this->typeInfo->getInputType();
     }
 
     /**
@@ -279,16 +279,16 @@ class ValidationContext
      */
     function getFieldDef()
     {
-        return $this->_typeInfo->getFieldDef();
+        return $this->typeInfo->getFieldDef();
     }
 
     function getDirective()
     {
-        return $this->_typeInfo->getDirective();
+        return $this->typeInfo->getDirective();
     }
 
     function getArgument()
     {
-        return $this->_typeInfo->getArgument();
+        return $this->typeInfo->getArgument();
     }
 }