diff --git a/includes/gateways/paypal/class-wc-gateway-paypal.php b/includes/gateways/paypal/class-wc-gateway-paypal.php
index d3d1bd6b461..7d0ce897776 100644
--- a/includes/gateways/paypal/class-wc-gateway-paypal.php
+++ b/includes/gateways/paypal/class-wc-gateway-paypal.php
@@ -1,9 +1,4 @@
 <?php
-
-if ( ! defined( 'ABSPATH' ) ) {
-	exit;
-}
-
 /**
  * PayPal Standard Payment Gateway.
  *
@@ -15,6 +10,14 @@ if ( ! defined( 'ABSPATH' ) ) {
  * @package		WooCommerce/Classes/Payment
  * @author 		WooThemes
  */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * WC_Gateway_Paypal Class.
+ */
 class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/** @var boolean Whether or not logging is enabled */
@@ -41,7 +44,7 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 		$this->init_form_fields();
 		$this->init_settings();
 
-		// Define user set variables
+		// Define user set variables.
 		$this->title          = $this->get_option( 'title' );
 		$this->description    = $this->get_option( 'description' );
 		$this->testmode       = 'yes' === $this->get_option( 'testmode', 'no' );
@@ -69,7 +72,7 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/**
 	 * Logging method.
-	 * @param  string $message
+	 * @param string $message
 	 */
 	public static function log( $message ) {
 		if ( self::$log_enabled ) {
@@ -82,7 +85,6 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/**
 	 * get_icon function.
-	 *
 	 * @return string
 	 */
 	public function get_icon() {
@@ -181,7 +183,6 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/**
 	 * Check if this gateway is enabled and available in the user's country.
-	 *
 	 * @return bool
 	 */
 	public function is_valid_for_use() {
@@ -213,9 +214,7 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/**
 	 * Get the transaction URL.
-	 *
 	 * @param  WC_Order $order
-	 *
 	 * @return string
 	 */
 	public function get_transaction_url( $order ) {
@@ -229,8 +228,7 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/**
 	 * Process the payment and return the result.
-	 *
-	 * @param int $order_id
+	 * @param  int $order_id
 	 * @return array
 	 */
 	public function process_payment( $order_id ) {
@@ -256,10 +254,10 @@ class WC_Gateway_Paypal extends WC_Payment_Gateway {
 
 	/**
 	 * Process a refund if supported.
-	 * @param  int $order_id
-	 * @param  float $amount
+	 * @param  int    $order_id
+	 * @param  float  $amount
 	 * @param  string $reason
-	 * @return  boolean True or false based on success, or a WP_Error object
+	 * @return boolean True or false based on success, or a WP_Error object
 	 */
 	public function process_refund( $order_id, $amount = null, $reason = '' ) {
 		$order = wc_get_order( $order_id );
diff --git a/includes/gateways/paypal/includes/class-wc-gateway-paypal-ipn-handler.php b/includes/gateways/paypal/includes/class-wc-gateway-paypal-ipn-handler.php
index cb56d118500..e8977fb7212 100644
--- a/includes/gateways/paypal/includes/class-wc-gateway-paypal-ipn-handler.php
+++ b/includes/gateways/paypal/includes/class-wc-gateway-paypal-ipn-handler.php
@@ -1,7 +1,7 @@
 <?php
 
 if ( ! defined( 'ABSPATH' ) ) {
-	exit; // Exit if accessed directly
+	exit;
 }
 
 include_once( 'class-wc-gateway-paypal-response.php' );
@@ -32,10 +32,11 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 		if ( ! empty( $_POST ) && $this->validate_ipn() ) {
 			$posted = wp_unslash( $_POST );
 
-			do_action( "valid-paypal-standard-ipn-request", $posted );
+			do_action( 'valid-paypal-standard-ipn-request', $posted );
 			exit;
 		}
-		wp_die( "PayPal IPN Request Failure", "PayPal IPN", array( 'response' => 500 ) );
+
+		wp_die( 'PayPal IPN Request Failure', 'PayPal IPN', array( 'response' => 500 ) );
 	}
 
 	/**
@@ -45,10 +46,10 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 	public function valid_response( $posted ) {
 		if ( ! empty( $posted['custom'] ) && ( $order = $this->get_paypal_order( $posted['custom'] ) ) ) {
 
-			// Lowercase returned variables
+			// Lowercase returned variables.
 			$posted['payment_status'] = strtolower( $posted['payment_status'] );
 
-			// Sandbox fix
+			// Sandbox fix.
 			if ( isset( $posted['test_ipn'] ) && 1 == $posted['test_ipn'] && 'pending' == $posted['payment_status'] ) {
 				$posted['payment_status'] = 'completed';
 			}
@@ -82,13 +83,13 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 			'user-agent'  => 'WooCommerce/' . WC()->version
 		);
 
-		// Post back to get a response
+		// Post back to get a response.
 		$response = wp_safe_remote_post( $this->sandbox ? 'https://www.sandbox.paypal.com/cgi-bin/webscr' : 'https://www.paypal.com/cgi-bin/webscr', $params );
 
 		WC_Gateway_Paypal::log( 'IPN Request: ' . print_r( $params, true ) );
 		WC_Gateway_Paypal::log( 'IPN Response: ' . print_r( $response, true ) );
 
-		// check to see if the request was valid
+		// Check to see if the request was valid.
 		if ( ! is_wp_error( $response ) && $response['response']['code'] >= 200 && $response['response']['code'] < 300 && strstr( $response['body'], 'VERIFIED' ) ) {
 			WC_Gateway_Paypal::log( 'Received valid response from PayPal' );
 			return true;
@@ -105,7 +106,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Check for a valid transaction type.
-	 * @param  string $txn_type
+	 * @param string $txn_type
 	 */
 	protected function validate_transaction_type( $txn_type ) {
 		$accepted_types = array( 'cart', 'instant', 'express_checkout', 'web_accept', 'masspay', 'send_money' );
@@ -118,15 +119,14 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Check currency from IPN matches the order.
-	 * @param  WC_Order $order
-	 * @param  string $currency
+	 * @param WC_Order $order
+	 * @param string $currency
 	 */
 	protected function validate_currency( $order, $currency ) {
-		// Validate currency
 		if ( $order->get_order_currency() != $currency ) {
 			WC_Gateway_Paypal::log( 'Payment error: Currencies do not match (sent "' . $order->get_order_currency() . '" | returned "' . $currency . '")' );
 
-			// Put this order on-hold for manual checking
+			// Put this order on-hold for manual checking.
 			$order->update_status( 'on-hold', sprintf( __( 'Validation error: PayPal currencies do not match (code %s).', 'woocommerce' ), $currency ) );
 			exit;
 		}
@@ -134,13 +134,13 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Check payment amount from IPN matches the order.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function validate_amount( $order, $amount ) {
 		if ( number_format( $order->get_total(), 2, '.', '' ) != number_format( $amount, 2, '.', '' ) ) {
 			WC_Gateway_Paypal::log( 'Payment error: Amounts do not match (gross ' . $amount . ')' );
 
-			// Put this order on-hold for manual checking
+			// Put this order on-hold for manual checking.
 			$order->update_status( 'on-hold', sprintf( __( 'Validation error: PayPal amounts do not match (gross %s).', 'woocommerce' ), $amount ) );
 			exit;
 		}
@@ -149,22 +149,21 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 	/**
 	 * Check receiver email from PayPal. If the receiver email in the IPN is different than what is stored in.
 	 * WooCommerce -> Settings -> Checkout -> PayPal, it will log an error about it.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function validate_receiver_email( $order, $receiver_email ) {
 		if ( strcasecmp( trim( $receiver_email ), trim( $this->receiver_email ) ) != 0 ) {
 			WC_Gateway_Paypal::log( "IPN Response is for another account: {$receiver_email}. Your email is {$this->receiver_email}" );
 
-			// Put this order on-hold for manual checking
+			// Put this order on-hold for manual checking.
 			$order->update_status( 'on-hold', sprintf( __( 'Validation error: PayPal IPN response from a different email address (%s).', 'woocommerce' ), $receiver_email ) );
-
 			exit;
 		}
 	}
 
 	/**
 	 * Handle a completed payment.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_completed( $order, $posted ) {
 		if ( $order->has_status( 'completed' ) ) {
@@ -182,7 +181,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 			$this->payment_complete( $order, ( ! empty( $posted['txn_id'] ) ? wc_clean( $posted['txn_id'] ) : '' ), __( 'IPN payment completed', 'woocommerce' ) );
 
 			if ( ! empty( $posted['mc_fee'] ) ) {
-				// log paypal transaction fee
+				// Log paypal transaction fee.
 				update_post_meta( $order->id, 'PayPal Transaction Fee', wc_clean( $posted['mc_fee'] ) );
 			}
 
@@ -193,7 +192,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a pending payment.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_pending( $order, $posted ) {
 		$this->payment_status_completed( $order, $posted );
@@ -201,7 +200,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a failed payment.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_failed( $order, $posted ) {
 		$order->update_status( 'failed', sprintf( __( 'Payment %s via IPN.', 'woocommerce' ), wc_clean( $posted['payment_status'] ) ) );
@@ -209,7 +208,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a denied payment.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_denied( $order, $posted ) {
 		$this->payment_status_failed( $order, $posted );
@@ -217,7 +216,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle an expired payment.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_expired( $order, $posted ) {
 		$this->payment_status_failed( $order, $posted );
@@ -225,7 +224,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a voided payment.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_voided( $order, $posted ) {
 		$this->payment_status_failed( $order, $posted );
@@ -233,13 +232,13 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a refunded order.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_refunded( $order, $posted ) {
-		// Only handle full refunds, not partial
+		// Only handle full refunds, not partial.
 		if ( $order->get_total() == ( $posted['mc_gross'] * -1 ) ) {
 
-			// Mark order as refunded
+			// Mark order as refunded.
 			$order->update_status( 'refunded', sprintf( __( 'Payment %s via IPN.', 'woocommerce' ), strtolower( $posted['payment_status'] ) ) );
 
 			$this->send_ipn_email_notification(
@@ -251,7 +250,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a reveral.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_reversed( $order, $posted ) {
 		$order->update_status( 'on-hold', sprintf( __( 'Payment %s via IPN.', 'woocommerce' ), wc_clean( $posted['payment_status'] ) ) );
@@ -264,7 +263,7 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Handle a cancelled reveral.
-	 * @param  WC_Order $order
+	 * @param WC_Order $order
 	 */
 	protected function payment_status_canceled_reversal( $order, $posted ) {
 		$this->send_ipn_email_notification(
@@ -294,8 +293,8 @@ class WC_Gateway_Paypal_IPN_Handler extends WC_Gateway_Paypal_Response {
 
 	/**
 	 * Send a notification to the user handling orders.
-	 * @param  string $subject
-	 * @param  string $message
+	 * @param string $subject
+	 * @param string $message
 	 */
 	protected function send_ipn_email_notification( $subject, $message ) {
 		$new_order_settings = get_option( 'woocommerce_new_order_settings', array() );
diff --git a/includes/gateways/paypal/includes/class-wc-gateway-paypal-pdt-handler.php b/includes/gateways/paypal/includes/class-wc-gateway-paypal-pdt-handler.php
index 124a6a4d96d..d0e9abfb69a 100644
--- a/includes/gateways/paypal/includes/class-wc-gateway-paypal-pdt-handler.php
+++ b/includes/gateways/paypal/includes/class-wc-gateway-paypal-pdt-handler.php
@@ -1,7 +1,7 @@
 <?php
 
 if ( ! defined( 'ABSPATH' ) ) {
-	exit; // Exit if accessed directly
+	exit;
 }
 
 include_once( 'class-wc-gateway-paypal-response.php' );
@@ -41,7 +41,7 @@ class WC_Gateway_Paypal_PDT_Handler extends WC_Gateway_Paypal_Response {
 			'user-agent'	=> 'WooCommerce/' . WC_VERSION
 		);
 
-		// Post back to get a response
+		// Post back to get a response.
 		$response = wp_safe_remote_post( $this->sandbox ? 'https://www.sandbox.paypal.com/cgi-bin/webscr' : 'https://www.paypal.com/cgi-bin/webscr', $pdt );
 
 		if ( is_wp_error( $response ) || ! strpos( $response['body'], "SUCCESS" ) === 0 ) {
@@ -76,7 +76,7 @@ class WC_Gateway_Paypal_PDT_Handler extends WC_Gateway_Paypal_Response {
 				$this->payment_complete( $order, $transaction,  __( 'PDT payment completed', 'woocommerce' ) );
 
 				if ( ! empty( $_REQUEST['mc_fee'] ) ) {
-					// log paypal transaction fee
+					// Log paypal transaction fee.
 					update_post_meta( $order->id, 'PayPal Transaction Fee', wc_clean( $_REQUEST['mc_fee'] ) );
 				}
 			}
diff --git a/includes/gateways/paypal/includes/class-wc-gateway-paypal-refund.php b/includes/gateways/paypal/includes/class-wc-gateway-paypal-refund.php
index 359a2ed34c2..3e4a0e4e89f 100644
--- a/includes/gateways/paypal/includes/class-wc-gateway-paypal-refund.php
+++ b/includes/gateways/paypal/includes/class-wc-gateway-paypal-refund.php
@@ -1,11 +1,11 @@
 <?php
 
 if ( ! defined( 'ABSPATH' ) ) {
-	exit; // Exit if accessed directly
+	exit;
 }
 
 /**
- * Handles refunds.
+ * Handles Refunds.
  */
 class WC_Gateway_Paypal_Refund {
 
@@ -21,8 +21,8 @@ class WC_Gateway_Paypal_Refund {
 	/**
 	 * Get refund request args.
 	 * @param  WC_Order $order
-	 * @param  float $amount
-	 * @param  string $reason
+	 * @param  float    $amount
+	 * @param  string   $reason
 	 * @return array
 	 */
 	public static function get_request( $order, $amount = null, $reason = '' ) {
@@ -47,9 +47,9 @@ class WC_Gateway_Paypal_Refund {
 	/**
 	 * Refund an order via PayPal.
 	 * @param  WC_Order $order
-	 * @param  float $amount
-	 * @param  string $reason
-	 * @param  boolean $sandbox
+	 * @param  float    $amount
+	 * @param  string   $reason
+	 * @param  boolean  $sandbox
 	 * @return array|wp_error The parsed response from paypal, or a WP_Error object
 	 */
 	public static function refund_order( $order, $amount = null, $reason = '', $sandbox = false ) {
diff --git a/includes/gateways/paypal/includes/class-wc-gateway-paypal-request.php b/includes/gateways/paypal/includes/class-wc-gateway-paypal-request.php
index df9dae75286..6340fdf4eb3 100644
--- a/includes/gateways/paypal/includes/class-wc-gateway-paypal-request.php
+++ b/includes/gateways/paypal/includes/class-wc-gateway-paypal-request.php
@@ -1,7 +1,7 @@
 <?php
 
 if ( ! defined( 'ABSPATH' ) ) {
-	exit; // Exit if accessed directly
+	exit;
 }
 
 /**
@@ -38,8 +38,8 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Get the PayPal request URL for an order.
-	 * @param  WC_Order  $order
-	 * @param  boolean $sandbox
+	 * @param  WC_Order $order
+	 * @param  boolean  $sandbox
 	 * @return string
 	 */
 	public function get_request_url( $order, $sandbox = false ) {
@@ -54,8 +54,7 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Get PayPal Args for passing to PP.
-	 *
-	 * @param WC_Order $order
+	 * @param  WC_Order $order
 	 * @return array
 	 */
 	protected function get_paypal_args( $order ) {
@@ -236,7 +235,6 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Get line items to send to paypal.
-	 *
 	 * @param  WC_Order $order
 	 * @return bool
 	 */
@@ -262,12 +260,12 @@ class WC_Gateway_Paypal_Request {
 			}
 		}
 
-		// Shipping Cost item - paypal only allows shipping per item, we want to send shipping for the order
+		// Shipping Cost item - paypal only allows shipping per item, we want to send shipping for the order.
 		if ( $order->get_total_shipping() > 0 && ! $this->add_line_item( sprintf( __( 'Shipping via %s', 'woocommerce' ), $order->get_shipping_method() ), 1, $this->round( $order->get_total_shipping(), $order ) ) ) {
 			return false;
 		}
 
-		// Check for mismatched totals
+		// Check for mismatched totals.
 		if ( $this->number_format( $calculated_total + $order->get_total_tax() + $this->round( $order->get_total_shipping(), $order ) - $this->round( $order->get_total_discount(), $order ), $order ) != $this->number_format( $order->get_total(), $order ) ) {
 			return false;
 		}
@@ -277,10 +275,10 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Add PayPal Line Item.
-	 * @param string  $item_name
-	 * @param integer $quantity
-	 * @param integer $amount
-	 * @param string  $item_number
+	 * @param  string  $item_name
+	 * @param  integer $quantity
+	 * @param  integer $amount
+	 * @param  string  $item_number
 	 * @return bool successfully added or not
 	 */
 	protected function add_line_item( $item_name, $quantity = 1, $amount = 0, $item_number = '' ) {
@@ -320,9 +318,7 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Check if currency has decimals.
-	 *
 	 * @param  string $currency
-	 *
 	 * @return bool
 	 */
 	protected function currency_has_decimals( $currency ) {
@@ -335,10 +331,8 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Round prices.
-	 *
 	 * @param  double $price
 	 * @param  WC_Order $order
-	 *
 	 * @return double
 	 */
 	protected function round( $price, $order ) {
@@ -353,10 +347,8 @@ class WC_Gateway_Paypal_Request {
 
 	/**
 	 * Format prices.
-	 *
 	 * @param  float|int $price
 	 * @param  WC_Order $order
-	 *
 	 * @return string
 	 */
 	protected function number_format( $price, $order ) {
diff --git a/includes/gateways/paypal/includes/class-wc-gateway-paypal-response.php b/includes/gateways/paypal/includes/class-wc-gateway-paypal-response.php
index 8bbbdc71e3d..b2a9d585201 100644
--- a/includes/gateways/paypal/includes/class-wc-gateway-paypal-response.php
+++ b/includes/gateways/paypal/includes/class-wc-gateway-paypal-response.php
@@ -1,11 +1,11 @@
 <?php
 
 if ( ! defined( 'ABSPATH' ) ) {
-	exit; // Exit if accessed directly
+	exit;
 }
 
 /**
- * Handles refunds.
+ * Handles Responses.
  */
 abstract class WC_Gateway_Paypal_Response {
 
@@ -14,12 +14,11 @@ abstract class WC_Gateway_Paypal_Response {
 
 	/**
 	 * Get the order from the PayPal 'Custom' variable.
-	 *
 	 * @param  string $raw_custom JSON Data passed back by PayPal
 	 * @return bool|WC_Order object
 	 */
 	protected function get_paypal_order( $raw_custom ) {
-		// We have the data in the correct format, so get the order
+		// We have the data in the correct format, so get the order.
 		if ( ( $custom = json_decode( $raw_custom ) ) && is_object( $custom ) ) {
 			$order_id  = $custom->order_id;
 			$order_key = $custom->order_key;
@@ -29,14 +28,14 @@ abstract class WC_Gateway_Paypal_Response {
 			$order_id  = $custom[0];
 			$order_key = $custom[1];
 
-		// Nothing was found
+		// Nothing was found.
 		} else {
 			WC_Gateway_Paypal::log( 'Error: Order ID and key were not found in "custom".' );
 			return false;
 		}
 
 		if ( ! $order = wc_get_order( $order_id ) ) {
-			// We have an invalid $order_id, probably because invoice_prefix has changed
+			// We have an invalid $order_id, probably because invoice_prefix has changed.
 			$order_id = wc_get_order_id_by_order_key( $order_key );
 			$order    = wc_get_order( $order_id );
 		}
@@ -52,8 +51,8 @@ abstract class WC_Gateway_Paypal_Response {
 	/**
 	 * Complete order, add transaction ID and note.
 	 * @param  WC_Order $order
-	 * @param  string $txn_id
-	 * @param  string $note
+	 * @param  string   $txn_id
+	 * @param  string   $note
 	 */
 	protected function payment_complete( $order, $txn_id = '', $note = '' ) {
 		$order->add_order_note( $note );
@@ -63,7 +62,7 @@ abstract class WC_Gateway_Paypal_Response {
 	/**
 	 * Hold order and add note.
 	 * @param  WC_Order $order
-	 * @param  string $reason
+	 * @param  string   $reason
 	 */
 	protected function payment_on_hold( $order, $reason = '' ) {
 		$order->update_status( 'on-hold', $reason );