diff --git a/src/Mailgun/Connection/RestClient.php b/src/Mailgun/Connection/RestClient.php
index bab2acc..e5505f0 100644
--- a/src/Mailgun/Connection/RestClient.php
+++ b/src/Mailgun/Connection/RestClient.php
@@ -3,35 +3,61 @@
 namespace Mailgun\Connection;
 
 use Guzzle\Http\Client as Guzzle;
-use Mailgun\MailgunClient;
 
 use Mailgun\Connection\Exceptions\GenericHTTPError;
 use Guzzle\Http\QueryAggregator\DuplicateAggregator;
 use Guzzle\Http\QueryAggregator\PhpAggregator;
 use Mailgun\Connection\Exceptions\InvalidCredentials;
-use Mailgun\Connection\Exceptions\NoDomainsConfigured;
 use Mailgun\Connection\Exceptions\MissingRequiredParameters;
 use Mailgun\Connection\Exceptions\MissingEndpoint;
+use Mailgun\Constants\Api;
+use Mailgun\Constants\ExceptionMessages;
 
-/*
-   This class is a wrapper for the Guzzle (HTTP Client Library).
-*/
-
-class RestClient{
+/**
+ * This class is a wrapper for the Guzzle (HTTP Client Library).
+ */
+class RestClient {
 
+    /**
+     * @var string
+     */
 	private $apiKey;
+
+    /**
+     * @var Guzzle
+     */
 	protected $mgClient;
+
+    /**
+     * @var bool
+     */
 	protected $hasFiles = False;
 
+    /**
+     * @param string $apiKey
+     * @param string $apiEndpoint
+     * @param string $apiVersion
+     * @param bool $ssl
+     */
 	public function __construct($apiKey, $apiEndpoint, $apiVersion, $ssl){
 		$this->apiKey = $apiKey;
 		$this->mgClient = new Guzzle($this->generateEndpoint($apiEndpoint, $apiVersion, $ssl));
 		$this->mgClient->setDefaultOption('curl.options', array('CURLOPT_FORBID_REUSE' => true));
-		$this->mgClient->setDefaultOption('auth', array (API_USER, $this->apiKey));
+		$this->mgClient->setDefaultOption('auth', array (Api::API_USER, $this->apiKey));
 		$this->mgClient->setDefaultOption('exceptions', false);
-		$this->mgClient->setUserAgent(SDK_USER_AGENT . '/' . SDK_VERSION);
+		$this->mgClient->setUserAgent(Api::SDK_USER_AGENT . '/' . Api::SDK_VERSION);
 	}
 
+    /**
+     * @param string $endpointUrl
+     * @param array $postData
+     * @param array $files
+     * @return \stdClass
+     * @throws GenericHTTPError
+     * @throws InvalidCredentials
+     * @throws MissingEndpoint
+     * @throws MissingRequiredParameters
+     */
 	public function post($endpointUrl, $postData = array(), $files = array()){
 		$request = $this->mgClient->post($endpointUrl, array(), $postData);
 
@@ -90,6 +116,15 @@ class RestClient{
 		return $this->responseHandler($response);
 	}
 
+    /**
+     * @param string $endpointUrl
+     * @param array $queryString
+     * @return \stdClass
+     * @throws GenericHTTPError
+     * @throws InvalidCredentials
+     * @throws MissingEndpoint
+     * @throws MissingRequiredParameters
+     */
 	public function get($endpointUrl, $queryString = array()){
 		$request = $this->mgClient->get($endpointUrl);
 		if(isset($queryString)){
@@ -101,12 +136,29 @@ class RestClient{
 		return $this->responseHandler($response);
 	}
 
+    /**
+     * @param string $endpointUrl
+     * @return \stdClass
+     * @throws GenericHTTPError
+     * @throws InvalidCredentials
+     * @throws MissingEndpoint
+     * @throws MissingRequiredParameters
+     */
 	public function delete($endpointUrl){
 		$request = $this->mgClient->delete($endpointUrl);
 		$response = $request->send();
 		return $this->responseHandler($response);
 	}
 
+    /**
+     * @param string $endpointUrl
+     * @param array $putData
+     * @return \stdClass
+     * @throws GenericHTTPError
+     * @throws InvalidCredentials
+     * @throws MissingEndpoint
+     * @throws MissingRequiredParameters
+     */
 	public function put($endpointUrl, $putData){
 		$request = $this->mgClient->put($endpointUrl, array(), $putData);
 		$request->getPostFields()->setAggregator(new DuplicateAggregator());
@@ -114,6 +166,14 @@ class RestClient{
 		return $this->responseHandler($response);
 	}
 
+    /**
+     * @param \Guzzle\Http\Message\Response $responseObj
+     * @return \stdClass
+     * @throws GenericHTTPError
+     * @throws InvalidCredentials
+     * @throws MissingEndpoint
+     * @throws MissingRequiredParameters
+     */
 	public function responseHandler($responseObj){
 		$httpResponseCode = $responseObj->getStatusCode();
 		if($httpResponseCode === 200){
@@ -124,21 +184,27 @@ class RestClient{
 			$result->http_response_body = $data && $jsonResponseData === null ? $data : $jsonResponseData;
 		}
 		elseif($httpResponseCode == 400){
-			throw new MissingRequiredParameters(EXCEPTION_MISSING_REQUIRED_PARAMETERS);
+			throw new MissingRequiredParameters(ExceptionMessages::EXCEPTION_MISSING_REQUIRED_PARAMETERS);
 		}
 		elseif($httpResponseCode == 401){
-			throw new InvalidCredentials(EXCEPTION_INVALID_CREDENTIALS);
+			throw new InvalidCredentials(ExceptionMessages::EXCEPTION_INVALID_CREDENTIALS);
 		}
 		elseif($httpResponseCode == 404){
-			throw new MissingEndpoint(EXCEPTION_MISSING_ENDPOINT);
+			throw new MissingEndpoint(ExceptionMessages::EXCEPTION_MISSING_ENDPOINT);
 		}
 		else{
-			throw new GenericHTTPError(EXCEPTION_GENERIC_HTTP_ERROR, $httpResponseCode, $responseObj->getBody());
+			throw new GenericHTTPError(ExceptionMessages::EXCEPTION_GENERIC_HTTP_ERROR, $httpResponseCode, $responseObj->getBody());
 		}
 		$result->http_response_code = $httpResponseCode;
 		return $result;
 	}
 
+    /**
+     * @param string $apiEndpoint
+     * @param string $apiVersion
+     * @param bool $ssl
+     * @return string
+     */
 	private function generateEndpoint($apiEndpoint, $apiVersion, $ssl){
 		if(!$ssl){
 			return "http://" . $apiEndpoint . "/" . $apiVersion . "/";
diff --git a/src/Mailgun/Constants/Api.php b/src/Mailgun/Constants/Api.php
new file mode 100644
index 0000000..7a2908e
--- /dev/null
+++ b/src/Mailgun/Constants/Api.php
@@ -0,0 +1,16 @@
+<?php
+
+
+namespace Mailgun\Constants;
+
+
+class Api {
+    const API_USER = "api";
+    const SDK_VERSION = "1.7";
+    const SDK_USER_AGENT = "mailgun-sdk-php";
+    const RECIPIENT_COUNT_LIMIT = 1000;
+    const CAMPAIGN_ID_LIMIT = 3;
+    const TAG_LIMIT = 3;
+    const DEFAULT_TIME_ZONE = "UTC";
+}
+ 
\ No newline at end of file
diff --git a/src/Mailgun/Constants/Constants.php b/src/Mailgun/Constants/Constants.php
deleted file mode 100644
index 6d69195..0000000
--- a/src/Mailgun/Constants/Constants.php
+++ /dev/null
@@ -1,23 +0,0 @@
-<?PHP
-
-const API_USER = "api";
-const SDK_VERSION = "1.7";
-const SDK_USER_AGENT = "mailgun-sdk-php";
-const RECIPIENT_COUNT_LIMIT = 1000;
-const CAMPAIGN_ID_LIMIT = 3;
-const TAG_LIMIT = 3;
-const DEFAULT_TIME_ZONE = "UTC";
-
-//Common Exception Messages
-const EXCEPTION_INVALID_CREDENTIALS = "Your credentials are incorrect.";
-const EXCEPTION_GENERIC_HTTP_ERROR = "An HTTP Error has occurred! Check your network connection and try again.";
-const EXCEPTION_MISSING_REQUIRED_PARAMETERS = "The parameters passed to the API were invalid. Check your inputs!";
-const EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS = "The parameters passed to the API were invalid. Check your inputs!";
-const EXCEPTION_MISSING_ENDPOINT = "The endpoint you've tried to access does not exist. Check your URL.";
-const TOO_MANY_RECIPIENTS = "You've exceeded the maximum recipient count (1,000) on the to field with autosend disabled.";
-const INVALID_PARAMETER_NON_ARRAY = "The parameter you've passed in position 2 must be an array.";
-const INVALID_PARAMETER_ATTACHMENT = "Attachments must be passed with an \"@\" preceding the file path. Web resources not supported.";
-const INVALID_PARAMETER_INLINE = "Inline images must be passed with an \"@\" preceding the file path. Web resources not supported.";
-const TOO_MANY_PARAMETERS_CAMPAIGNS = "You've exceeded the maximum (3) campaigns for a single message.";
-const TOO_MANY_PARAMETERS_TAGS = "You've exceeded the maximum (3) tags for a single message.";
-const TOO_MANY_PARAMETERS_RECIPIENT = "You've exceeded the maximum recipient count (1,000) on the to field with autosend disabled.";
diff --git a/src/Mailgun/Constants/ExceptionMessages.php b/src/Mailgun/Constants/ExceptionMessages.php
new file mode 100644
index 0000000..8850041
--- /dev/null
+++ b/src/Mailgun/Constants/ExceptionMessages.php
@@ -0,0 +1,21 @@
+<?php
+
+
+namespace Mailgun\Constants;
+
+
+class ExceptionMessages {
+    const EXCEPTION_INVALID_CREDENTIALS = "Your credentials are incorrect.";
+    const EXCEPTION_GENERIC_HTTP_ERROR = "An HTTP Error has occurred! Check your network connection and try again.";
+    const EXCEPTION_MISSING_REQUIRED_PARAMETERS = "The parameters passed to the API were invalid. Check your inputs!";
+    const EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS = "The parameters passed to the API were invalid. Check your inputs!";
+    const EXCEPTION_MISSING_ENDPOINT = "The endpoint you've tried to access does not exist. Check your URL.";
+    const TOO_MANY_RECIPIENTS = "You've exceeded the maximum recipient count (1,000) on the to field with autosend disabled.";
+    const INVALID_PARAMETER_NON_ARRAY = "The parameter you've passed in position 2 must be an array.";
+    const INVALID_PARAMETER_ATTACHMENT = "Attachments must be passed with an \"@\" preceding the file path. Web resources not supported.";
+    const INVALID_PARAMETER_INLINE = "Inline images must be passed with an \"@\" preceding the file path. Web resources not supported.";
+    const TOO_MANY_PARAMETERS_CAMPAIGNS = "You've exceeded the maximum (3) campaigns for a single message.";
+    const TOO_MANY_PARAMETERS_TAGS = "You've exceeded the maximum (3) tags for a single message.";
+    const TOO_MANY_PARAMETERS_RECIPIENT = "You've exceeded the maximum recipient count (1,000) on the to field with autosend disabled.";
+}
+ 
\ No newline at end of file
diff --git a/src/Mailgun/Lists/OptInHandler.php b/src/Mailgun/Lists/OptInHandler.php
index 3037dcc..d929134 100644
--- a/src/Mailgun/Lists/OptInHandler.php
+++ b/src/Mailgun/Lists/OptInHandler.php
@@ -6,17 +6,20 @@ use Mailgun\Messages\Exceptions\InvalidParameter;
 use Mailgun\Messages\Exceptions\TooManyParameters;
 use Mailgun\Messages\Expcetions\InvalidParameterType;
 
-/* 
-   This class is used for creating a unique hash for 
-   mailing list subscription double-opt in requests.
-*/
-
+/**
+ * This class is used for creating a unique hash for
+ * mailing list subscription double-opt in requests.
+ *
+ * @link https://github.com/mailgun/mailgun-php/blob/master/src/Mailgun/Lists/README.md
+ */
 class OptInHandler{
 
-	function __construct(){
-		
-	}
-	
+    /**
+     * @param string $mailingList
+     * @param string $secretAppId
+     * @param string $recipientAddress
+     * @return string
+     */
 	public function generateHash($mailingList, $secretAppId, $recipientAddress){
 		$innerPayload = array('r' => $recipientAddress, 'l' => $mailingList);
 		$encodedInnerPayload = base64_encode(json_encode($innerPayload));
@@ -27,6 +30,11 @@ class OptInHandler{
 		return urlencode(base64_encode(json_encode($outerPayload)));
 	}
 
+    /**
+     * @param string $secretAppId
+     * @param string $uniqueHash
+     * @return array|bool
+     */
 	public function validateHash($secretAppId, $uniqueHash){
 		$decodedOuterPayload = json_decode(base64_decode(urldecode($uniqueHash)), true);
 
diff --git a/src/Mailgun/Mailgun.php b/src/Mailgun/Mailgun.php
index fc9224b..5dea5ad 100644
--- a/src/Mailgun/Mailgun.php
+++ b/src/Mailgun/Mailgun.php
@@ -2,36 +2,53 @@
 
 namespace Mailgun;
 
-require_once 'Constants/Constants.php';
-
-use Mailgun\Messages\Messages;
+use Mailgun\Constants\ExceptionMessages;
 use Mailgun\Messages\Exceptions;
 use Mailgun\Connection\RestClient;
 use Mailgun\Messages\BatchMessage;
 use Mailgun\Lists\OptInHandler;
 use Mailgun\Messages\MessageBuilder;
 
-/*
-   This class is the base class for the Mailgun SDK.
-   See the official documentation for usage instructions.
-*/
-
+/**
+ * This class is the base class for the Mailgun SDK.
+ * See the official documentation (link below) for usage instructions.
+ *
+ * @link https://github.com/mailgun/mailgun-php/blob/master/README.md
+ */
 class Mailgun{
-    protected $workingDomain;
+
+    /**
+     * @var RestClient
+     */
     protected $restClient;
+
+    /**
+     * @var null|string
+     */
     protected $apiKey;
-    
+
+    /**
+     * @param string|null $apiKey
+     * @param string $apiEndpoint
+     * @param string $apiVersion
+     * @param bool $ssl
+     */
     public function __construct($apiKey = null, $apiEndpoint = "api.mailgun.net", $apiVersion = "v2", $ssl = true){
         $this->apiKey = $apiKey;
         $this->restClient = new RestClient($apiKey, $apiEndpoint, $apiVersion, $ssl);
     }
 
+    /**
+     *  This function allows the sending of a fully formed message OR a custom
+     *  MIME string. If sending MIME, the string must be passed in to the 3rd
+     *  position of the function call.
+     *
+     * @param string $workingDomain
+     * @param array $postData
+     * @param array $postFiles
+     * @throws Exceptions\MissingRequiredMIMEParameters
+     */
     public function sendMessage($workingDomain, $postData, $postFiles = array()){
-        /*
-         *  This function allows the sending of a fully formed message OR a custom
-         *  MIME string. If sending MIME, the string must be passed in to the 3rd
-         *  position of the function call.
-        */
         if(is_array($postFiles)){
             return $this->post("$workingDomain/messages", $postData, $postFiles);
         }
@@ -47,21 +64,24 @@ class Mailgun{
             return $result;
         }
         else{
-            throw new Exceptions\MissingRequiredMIMEParameters(EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
+            throw new Exceptions\MissingRequiredMIMEParameters(ExceptionMessages::EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
         }
     }
-    
+
+    /**
+     * This function checks the signature in a POST request to see if it is
+     * authentic.
+     *
+     * Pass an array of parameters.  If you pass nothing, $_POST will be
+     * used instead.
+     *
+     * If this function returns FALSE, you must not process the request.
+     * You should reject the request with status code 403 Forbidden.
+     *
+     * @param array|null $postData
+     * @return bool
+     */
     public function verifyWebhookSignature($postData = NULL) {
-        /*
-         * This function checks the signature in a POST request to see if it is
-         * authentic.
-         *
-         * Pass an array of parameters.  If you pass nothing, $_POST will be
-         * used instead.
-         *
-         * If this function returns FALSE, you must not process the request.
-         * You should reject the request with status code 403 Forbidden.
-        */
         if(is_null($postData)) {
             $postData = $_POST;
         }
@@ -76,30 +96,61 @@ class Mailgun{
         }
     }
 
+    /**
+     * @param string $endpointUrl
+     * @param array $postData
+     * @param array $files
+     * @return \stdClass
+     */
     public function post($endpointUrl, $postData = array(), $files = array()){
         return $this->restClient->post($endpointUrl, $postData, $files);
     }
 
+    /**
+     * @param string $endpointUrl
+     * @param array $queryString
+     * @return \stdClass
+     */
     public function get($endpointUrl, $queryString = array()){
         return $this->restClient->get($endpointUrl, $queryString);
     }
 
+    /**
+     * @param string $endpointUrl
+     * @return \stdClass
+     */
     public function delete($endpointUrl){
         return $this->restClient->delete($endpointUrl);
     }
 
+    /**
+     * @param string $endpointUrl
+     * @param array $putData
+     * @return \stdClass
+     */
     public function put($endpointUrl, $putData){
         return $this->restClient->put($endpointUrl, $putData);
     }
 
+    /**
+     * @return MessageBuilder
+     */
     public function MessageBuilder(){
         return new MessageBuilder();
     }
 
+    /**
+     * @return OptInHandler
+     */
     public function OptInHandler(){
         return new OptInHandler();
     }
 
+    /**
+     * @param string $workingDomain
+     * @param bool $autoSend
+     * @return BatchMessage
+     */
     public function BatchMessage($workingDomain, $autoSend = true){
         return new BatchMessage($this->restClient, $workingDomain, $autoSend);
     }
diff --git a/src/Mailgun/Messages/BatchMessage.php b/src/Mailgun/Messages/BatchMessage.php
index 834089a..003178e 100644
--- a/src/Mailgun/Messages/BatchMessage.php
+++ b/src/Mailgun/Messages/BatchMessage.php
@@ -2,23 +2,49 @@
 
 namespace Mailgun\Messages;
 
-use Mailgun\Messages\MessageBuilder;
+use Mailgun\Constants\Api;
+use Mailgun\Constants\ExceptionMessages;
 use Mailgun\Messages\Exceptions\TooManyParameters;
 use Mailgun\Messages\Exceptions\MissingRequiredMIMEParameters;
 
-/*
-   This class is used for batch sending. See the official documentation
-   for usage instructions.
-*/
-
+/**
+ * This class is used for batch sending. See the official documentation (link below)
+ * for usage instructions.
+ *
+ * @link https://github.com/mailgun/mailgun-php/blob/master/src/Mailgun/Messages/README.md
+ */
 class BatchMessage extends MessageBuilder{
 
+    /**
+     * @var array
+     */
 	private $batchRecipientAttributes;
+
+    /**
+     * @var boolean
+     */
 	private $autoSend;
+
+    /**
+     * @var \Mailgun\Connection\RestClient
+     */
 	private $restClient;
+
+    /**
+     * @var string
+     */
 	private $workingDomain;
+
+    /**
+     * @var array
+     */
 	private $messageIds = array();
 
+    /**
+     * @param \Mailgun\Connection\RestClient $restClient
+     * @param string $workingDomain
+     * @param boolean $autoSend
+     */
 	public function __construct($restClient, $workingDomain, $autoSend){
 		$this->batchRecipientAttributes = array();
 		$this->autoSend = $autoSend;
@@ -27,11 +53,18 @@ class BatchMessage extends MessageBuilder{
 		$this->endpointUrl = $workingDomain . "/messages";
 	}
 
+    /**
+     * @param string $headerName
+     * @param string $address
+     * @param array $variables
+     * @throws MissingRequiredMIMEParameters
+     * @throws TooManyParameters
+     */
 	protected function addRecipient($headerName, $address, $variables){
 		if(array_key_exists($headerName, $this->counters['recipients'])){
-			if($this->counters['recipients'][$headerName] == RECIPIENT_COUNT_LIMIT){
+			if($this->counters['recipients'][$headerName] == Api::RECIPIENT_COUNT_LIMIT){
 				if($this->autoSend == false){
-					throw new TooManyParameters(TOO_MANY_RECIPIENTS);
+					throw new TooManyParameters(ExceptionMessages::TOO_MANY_RECIPIENTS);
 				}
 				$this->sendMessage();
 			}
@@ -58,22 +91,27 @@ class BatchMessage extends MessageBuilder{
 		$this->batchRecipientAttributes["$address"] = $variables;
 	}
 
+    /**
+     * @param array $message
+     * @param array $files
+     * @throws MissingRequiredMIMEParameters
+     */
 	public function sendMessage($message = array(), $files = array()){
 		if(count($message) < 1){
 			$message = $this->message;
 			$files = $this->files;
 		}
 		if(!array_key_exists("from", $message)){
-			throw new MissingRequiredMIMEParameters(EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
+			throw new MissingRequiredMIMEParameters(ExceptionMessages::EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
 		}
 		elseif(!array_key_exists("to", $message)){
-			throw new MissingRequiredMIMEParameters(EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
+			throw new MissingRequiredMIMEParameters(ExceptionMessages::EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
 		}
 		elseif(!array_key_exists("subject", $message)){
-			throw new MissingRequiredMIMEParameters(EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
+			throw new MissingRequiredMIMEParameters(ExceptionMessages::EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
 		}
 		elseif((!array_key_exists("text", $message) && !array_key_exists("html", $message))){
-			throw new MissingRequiredMIMEParameters(EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
+			throw new MissingRequiredMIMEParameters(ExceptionMessages::EXCEPTION_MISSING_REQUIRED_MIME_PARAMETERS);
 		}
 		else{
 			$message["recipient-variables"] = json_encode($this->batchRecipientAttributes);
@@ -87,10 +125,16 @@ class BatchMessage extends MessageBuilder{
 		}
 	}
 
+    /**
+     * @throws MissingRequiredMIMEParameters
+     */
 	public function finalize(){
-		return $this->sendMessage();
+		$this->sendMessage();
 	}
 
+    /**
+     * @return string[]
+     */
 	public function getMessageIds(){
 		return $this->messageIds;
 	}
diff --git a/src/Mailgun/Messages/MessageBuilder.php b/src/Mailgun/Messages/MessageBuilder.php
index 34032bb..1ee5d83 100644
--- a/src/Mailgun/Messages/MessageBuilder.php
+++ b/src/Mailgun/Messages/MessageBuilder.php
@@ -2,23 +2,39 @@
 
 namespace Mailgun\Messages;
 
+use Mailgun\Constants\Api;
+use Mailgun\Constants\ExceptionMessages;
 use Mailgun\Messages\Exceptions\InvalidParameter;
 use Mailgun\Messages\Exceptions\TooManyParameters;
-use Mailgun\Messages\Exceptions\InvalidParameterType;
-
-/*
-   This class is used for composing a properly formed
-   message object. Dealing with arrays can be cumbersome,
-   this class makes the process easier. See the official
-   documentation for usage instructions.
-*/
 
+/**
+ * This class is used for composing a properly formed
+ * message object. Dealing with arrays can be cumbersome,
+ * this class makes the process easier. See the official
+ * documentation (link below) for usage instructions.
+ *
+ * @link https://github.com/mailgun/mailgun-php/blob/master/src/Mailgun/Messages/README.md
+ */
 class MessageBuilder
 {
-
+    /**
+     * @var array
+     */
     protected $message = array();
+
+    /**
+     * @var array
+     */
     protected $variables = array();
+
+    /**
+     * @var array
+     */
     protected $files = array();
+
+    /**
+     * @var array
+     */
     protected $counters = array(
         'recipients' => array(
             'to'  => 0,
@@ -33,6 +49,12 @@ class MessageBuilder
         )
     );
 
+    /**
+     * @param array $params
+     * @param string $key
+     * @param mixed $default
+     * @return mixed
+     */
     protected function safeGet($params, $key, $default)
     {
         if (array_key_exists($key, $params)) {
@@ -42,6 +64,10 @@ class MessageBuilder
         return $default;
     }
 
+    /**
+     * @param array $params
+     * @return mixed|string
+     */
     protected function getFullName($params)
     {
         if (array_key_exists("first", $params)) {
@@ -54,6 +80,11 @@ class MessageBuilder
         return $this->safeGet($params, "full_name", "");
     }
 
+    /**
+     * @param string $address
+     * @param array $variables
+     * @return string
+     */
     protected function parseAddress($address, $variables)
     {
         if (!is_array($variables)) {
@@ -67,6 +98,11 @@ class MessageBuilder
         return $address;
     }
 
+    /**
+     * @param string $headerName
+     * @param string $address
+     * @param array $variables
+     */
     protected function addRecipient($headerName, $address, $variables)
     {
         $compiledAddress = $this->parseAddress($address, $variables);
@@ -83,36 +119,59 @@ class MessageBuilder
         }
     }
 
+    /**
+     * @param string $address
+     * @param array|null $variables
+     * @return mixed
+     * @throws TooManyParameters
+     */
     public function addToRecipient($address, $variables = null)
     {
-        if ($this->counters['recipients']['to'] > RECIPIENT_COUNT_LIMIT) {
-            throw new TooManyParameters(TOO_MANY_PARAMETERS_RECIPIENT);
+        if ($this->counters['recipients']['to'] > Api::RECIPIENT_COUNT_LIMIT) {
+            throw new TooManyParameters(ExceptionMessages::TOO_MANY_PARAMETERS_RECIPIENT);
         }
         $this->addRecipient("to", $address, $variables);
 
         return end($this->message['to']);
     }
 
+    /**
+     * @param string $address
+     * @param array|null $variables
+     * @return mixed
+     * @throws TooManyParameters
+     */
     public function addCcRecipient($address, $variables = null)
     {
-        if ($this->counters['recipients']['cc'] > RECIPIENT_COUNT_LIMIT) {
-            throw new TooManyParameters(TOO_MANY_PARAMETERS_RECIPIENT);
+        if ($this->counters['recipients']['cc'] > Api::RECIPIENT_COUNT_LIMIT) {
+            throw new TooManyParameters(ExceptionMessages::TOO_MANY_PARAMETERS_RECIPIENT);
         }
         $this->addRecipient("cc", $address, $variables);
 
         return end($this->message['cc']);
     }
 
+    /**
+     * @param string $address
+     * @param array|null $variables
+     * @return mixed
+     * @throws TooManyParameters
+     */
     public function addBccRecipient($address, $variables = null)
     {
-        if ($this->counters['recipients']['bcc'] > RECIPIENT_COUNT_LIMIT) {
-            throw new TooManyParameters(TOO_MANY_PARAMETERS_RECIPIENT);
+        if ($this->counters['recipients']['bcc'] > Api::RECIPIENT_COUNT_LIMIT) {
+            throw new TooManyParameters(ExceptionMessages::TOO_MANY_PARAMETERS_RECIPIENT);
         }
         $this->addRecipient("bcc", $address, $variables);
 
         return end($this->message['bcc']);
     }
 
+    /**
+     * @param string $address
+     * @param array|null $variables
+     * @return mixed
+     */
     public function setFromAddress($address, $variables = null)
     {
         $this->addRecipient("from", $address, $variables);
@@ -120,6 +179,11 @@ class MessageBuilder
         return $this->message['from'];
     }
 
+    /**
+     * @param string $address
+     * @param array|null $variables
+     * @return mixed
+     */
     public function setReplyToAddress($address, $variables = null)
     {
         $this->addRecipient("h:reply-to", $address, $variables);
@@ -127,7 +191,11 @@ class MessageBuilder
         return $this->message['h:reply-to'];
     }
 
-    public function setSubject($subject = null)
+    /**
+     * @param string $subject
+     * @return mixed
+     */
+    public function setSubject($subject = "")
     {
         if ($subject == null || $subject == "") {
             $subject = " ";
@@ -137,6 +205,11 @@ class MessageBuilder
         return $this->message['subject'];
     }
 
+    /**
+     * @param string $headerName
+     * @param mixed $headerData
+     * @return mixed
+     */
     public function addCustomHeader($headerName, $headerData)
     {
         if (!preg_match("/^h:/i", $headerName)) {
@@ -147,6 +220,10 @@ class MessageBuilder
         return $this->message[$headerName];
     }
 
+    /**
+     * @param string $textBody
+     * @return string
+     */
     public function setTextBody($textBody)
     {
         if ($textBody == null || $textBody == "") {
@@ -157,6 +234,10 @@ class MessageBuilder
         return $this->message['text'];
     }
 
+    /**
+     * @param string $htmlBody
+     * @return string
+     */
     public function setHtmlBody($htmlBody)
     {
         if ($htmlBody == null || $htmlBody == "") {
@@ -167,6 +248,11 @@ class MessageBuilder
         return $this->message['html'];
     }
 
+    /**
+     * @param string $attachmentPath
+     * @param string|null $attachmentName
+     * @return bool
+     */
     public function addAttachment($attachmentPath, $attachmentName = null)
     {
         if (isset($this->files["attachment"])) {
@@ -187,6 +273,11 @@ class MessageBuilder
         return true;
     }
 
+    /**
+     * @param string $inlineImagePath
+     * @param string|null $inlineImageName
+     * @throws InvalidParameter
+     */
     public function addInlineImage($inlineImagePath, $inlineImageName = null)
     {
         if (preg_match("/^@/", $inlineImagePath)) {
@@ -207,10 +298,14 @@ class MessageBuilder
 
             return true;
         } else {
-            throw new InvalidParameter(INVALID_PARAMETER_INLINE);
+            throw new InvalidParameter(ExceptionMessages::INVALID_PARAMETER_INLINE);
         }
     }
 
+    /**
+     * @param boolean $testMode
+     * @return string
+     */
     public function setTestMode($testMode)
     {
         if (filter_var($testMode, FILTER_VALIDATE_BOOLEAN)) {
@@ -223,9 +318,14 @@ class MessageBuilder
         return $this->message['o:testmode'];
     }
 
+    /**
+     * @param string|int $campaignId
+     * @return string|int
+     * @throws TooManyParameters
+     */
     public function addCampaignId($campaignId)
     {
-        if ($this->counters['attributes']['campaign_id'] < CAMPAIGN_ID_LIMIT) {
+        if ($this->counters['attributes']['campaign_id'] < Api::CAMPAIGN_ID_LIMIT) {
             if (isset($this->message['o:campaign'])) {
                 array_push($this->message['o:campaign'], $campaignId);
             } else {
@@ -235,13 +335,17 @@ class MessageBuilder
 
             return $this->message['o:campaign'];
         } else {
-            throw new TooManyParameters(TOO_MANY_PARAMETERS_CAMPAIGNS);
+            throw new TooManyParameters(ExceptionMessages::TOO_MANY_PARAMETERS_CAMPAIGNS);
         }
     }
 
+    /**
+     * @param string $tag
+     * @throws TooManyParameters
+     */
     public function addTag($tag)
     {
-        if ($this->counters['attributes']['tag'] < TAG_LIMIT) {
+        if ($this->counters['attributes']['tag'] < Api::TAG_LIMIT) {
             if (isset($this->message['o:tag'])) {
                 array_push($this->message['o:tag'], $tag);
             } else {
@@ -251,10 +355,14 @@ class MessageBuilder
 
             return $this->message['o:tag'];
         } else {
-            throw new TooManyParameters(TOO_MANY_PARAMETERS_TAGS);
+            throw new TooManyParameters(ExceptionMessages::TOO_MANY_PARAMETERS_TAGS);
         }
     }
 
+    /**
+     * @param boolean $enabled
+     * @return mixed
+     */
     public function setDkim($enabled)
     {
         if (filter_var($enabled, FILTER_VALIDATE_BOOLEAN)) {
@@ -267,6 +375,10 @@ class MessageBuilder
         return $this->message["o:dkim"];
     }
 
+    /**
+     * @param boolean $enabled
+     * @return string
+     */
     public function setOpenTracking($enabled)
     {
         if (filter_var($enabled, FILTER_VALIDATE_BOOLEAN)) {
@@ -279,6 +391,10 @@ class MessageBuilder
         return $this->message['o:tracking-opens'];
     }
 
+    /**
+     * @param boolean $enabled
+     * @return string
+     */
     public function setClickTracking($enabled)
     {
         if (filter_var($enabled, FILTER_VALIDATE_BOOLEAN)) {
@@ -293,12 +409,17 @@ class MessageBuilder
         return $this->message['o:tracking-clicks'];
     }
 
+    /**
+     * @param string $timeDate
+     * @param string|null $timeZone
+     * @return string
+     */
     public function setDeliveryTime($timeDate, $timeZone = null)
     {
         if (isset($timeZone)) {
             $timeZoneObj = new \DateTimeZone("$timeZone");
         } else {
-            $timeZoneObj = new \DateTimeZone(\DEFAULT_TIME_ZONE);
+            $timeZoneObj = new \DateTimeZone(Api::DEFAULT_TIME_ZONE);
         }
 
         $dateTimeObj                     = new \DateTime($timeDate, $timeZoneObj);
@@ -308,11 +429,20 @@ class MessageBuilder
         return $this->message['o:deliverytime'];
     }
 
+    /**
+     * @param string $customName
+     * @param mixed $data
+     */
     public function addCustomData($customName, $data)
     {
         $this->message['v:' . $customName] = json_encode($data);
     }
 
+    /**
+     * @param string $parameterName
+     * @param mixed $data
+     * @return mixed
+     */
     public function addCustomParameter($parameterName, $data)
     {
         if (isset($this->message[$parameterName])) {
@@ -326,16 +456,25 @@ class MessageBuilder
         }
     }
 
+    /**
+     * @param array $message
+     */
     public function setMessage($message)
     {
         $this->message = $message;
     }
 
+    /**
+     * @return array
+     */
     public function getMessage()
     {
         return $this->message;
     }
 
+    /**
+     * @return array
+     */
     public function getFiles()
     {
         return $this->files;