diff --git a/src/Error/Error.php b/src/Error/Error.php
index 5976e1c..e31ccf1 100644
--- a/src/Error/Error.php
+++ b/src/Error/Error.php
@@ -5,7 +5,6 @@ use GraphQL\Language\Source;
 use GraphQL\Language\SourceLocation;
 use GraphQL\Utils;
 
-
 /**
  * Class Error
  * A GraphQLError describes an Error found during the parse, validate, or
@@ -141,8 +140,12 @@ class Error extends \Exception implements \JsonSerializable
     {
         if (null === $this->positions) {
             if (!empty($this->nodes)) {
-                $positions = array_map(function($node) { return isset($node->loc) ? $node->loc->start : null; }, $this->nodes);
-                $this->positions = array_filter($positions, function($p) {return $p !== null;});
+                $positions = array_map(function($node) {
+                    return isset($node->loc) ? $node->loc->start : null;
+                }, $this->nodes);
+                $this->positions = array_filter($positions, function($p) {
+                    return $p !== null;
+                });
             }
         }
         return $this->positions;
diff --git a/src/Error/SyntaxError.php b/src/Error/SyntaxError.php
index 9fc2820..36bf7db 100644
--- a/src/Error/SyntaxError.php
+++ b/src/Error/SyntaxError.php
@@ -4,10 +4,6 @@ namespace GraphQL\Error;
 use GraphQL\Language\Source;
 use GraphQL\Language\SourceLocation;
 
-/**
- * Class SyntaxError
- * @package GraphQL\Error
- */
 class SyntaxError extends Error
 {
     /**
@@ -33,9 +29,9 @@ class SyntaxError extends Error
     public static function highlightSourceAtLocation(Source $source, SourceLocation $location)
     {
         $line = $location->line;
-        $prevLineNum = (string)($line - 1);
-        $lineNum = (string)$line;
-        $nextLineNum = (string)($line + 1);
+        $prevLineNum = (string) ($line - 1);
+        $lineNum = (string) $line;
+        $nextLineNum = (string) ($line + 1);
         $padLen = mb_strlen($nextLineNum, 'UTF-8');
 
         $unicodeChars = json_decode('"\u2028\u2029"'); // Quick hack to get js-compatible representation of these chars
diff --git a/src/Language/Printer.php b/src/Language/Printer.php
index e24f6b4..16b9bc5 100644
--- a/src/Language/Printer.php
+++ b/src/Language/Printer.php
@@ -42,11 +42,17 @@ class Printer
 {
     public function doPrint($ast)
     {
-        return Visitor::visit($ast, array(
-            'leave' => array(
-                Node::NAME => function($node) {return '' . $node->value;},
-                Node::VARIABLE => function($node) {return '$' . $node->name;},
-                Node::DOCUMENT => function(Document $node) {return $this->join($node->definitions, "\n\n") . "\n";},
+        return Visitor::visit($ast, [
+            'leave' => [
+                Node::NAME => function($node) {
+                    return '' . $node->value;
+                },
+                Node::VARIABLE => function($node) {
+                    return '$' . $node->name;
+                },
+                Node::DOCUMENT => function(Document $node) {
+                    return $this->join($node->definitions, "\n\n") . "\n";
+                },
                 Node::OPERATION_DEFINITION => function(OperationDefinition $node) {
                     $op = $node->operation;
                     $name = $node->name;
@@ -187,13 +193,15 @@ class Printer
                         $this->block($def->fields)
                     ], ' ');
                 },
-                Node::TYPE_EXTENSION_DEFINITION => function(TypeExtensionDefinition $def) {return "extend {$def->definition}";},
+                Node::TYPE_EXTENSION_DEFINITION => function(TypeExtensionDefinition $def) {
+                    return "extend {$def->definition}";
+                },
                 Node::DIRECTIVE_DEFINITION => function(DirectiveDefinition $def) {
                     return 'directive @' . $def->name . $this->wrap('(', $this->join($def->arguments, ', '), ')')
                         . ' on ' . $this->join($def->locations, ' | ');
                 }
-            )
-        ));
+            ]
+        ]);
     }
 
     /**
diff --git a/src/Language/Source.php b/src/Language/Source.php
index 1d3d335..5083f40 100644
--- a/src/Language/Source.php
+++ b/src/Language/Source.php
@@ -36,7 +36,7 @@ class Source
 
         $utfChars = json_decode('"\u2028\u2029"');
         $lineRegexp = '/\r\n|[\n\r'.$utfChars.']/su';
-        $matches = array();
+        $matches = [];
         preg_match_all($lineRegexp, mb_substr($this->body, 0, $position, 'UTF-8'), $matches, PREG_OFFSET_CAPTURE);
 
         foreach ($matches[0] as $index => $match) {
diff --git a/src/Language/Visitor.php b/src/Language/Visitor.php
index 4cf650f..1b0e714 100644
--- a/src/Language/Visitor.php
+++ b/src/Language/Visitor.php
@@ -38,7 +38,7 @@ class Visitor
         return $r;
     }
 
-    public static $visitorKeys = array(
+    public static $visitorKeys = [
         Node::NAME => [],
         Node::DOCUMENT => ['definitions'],
         Node::OPERATION_DEFINITION => ['name', 'variableDefinitions', 'directives', 'selectionSet'],
@@ -77,7 +77,7 @@ class Visitor
         Node::INPUT_OBJECT_TYPE_DEFINITION => [ 'name', 'directives', 'fields' ],
         Node::TYPE_EXTENSION_DEFINITION => [ 'definition' ],
         Node::DIRECTIVE_DEFINITION => [ 'name', 'arguments', 'locations' ]
-    );
+    ];
 
     /**
      * visit() will walk through an AST using a depth first traversal, calling
@@ -279,16 +279,16 @@ class Visitor
             }
 
             if (!$isLeaving) {
-                $stack = array(
+                $stack = [
                     'inArray' => $inArray,
                     'index' => $index,
                     'keys' => $keys,
                     'edits' => $edits,
                     'prev' => $stack
-                );
+                ];
                 $inArray = is_array($node);
 
-                $keys = ($inArray ? $node : $visitorKeys[$node->kind]) ?: array();
+                $keys = ($inArray ? $node : $visitorKeys[$node->kind]) ?: [];
                 $index = -1;
                 $edits = [];
                 if ($parent) {
diff --git a/src/Utils.php b/src/Utils.php
index 24912d1..17f32f0 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -11,10 +11,12 @@ class Utils
 {
     /**
      * @param object $obj
-     * @param array $vars
+     * @param array  $vars
+     * @param array  $requiredKeys
+     *
      * @return array
      */
-    public static function assign($obj, array $vars, array $requiredKeys = array())
+    public static function assign($obj, array $vars, array $requiredKeys = [])
     {
         foreach ($requiredKeys as $key) {
             if (!isset($key, $vars)) {