mandrill-wp-mail.php

<?php
/**
 * Plugin Name:  Mandrill wp_mail Drop-In
 * Plugin URI:   https://github.com/danielbachhuber/mandrill-wp-mail
 * Description:  Drop-in replacement for wp_mail using the Mandrill API.
 * Version:      0.0.2
 * Author:       Daniel Bachhuber
 * Author URI:   https://github.com/danielbachhuber
 * License:      GPL-2.0+
 * License URI:  http://www.gnu.org/licenses/gpl-2.0.html
 */

/**
 * Override WordPress' default wp_mail function with one that sends email
 * using Mandrill's API.
 *
 * Note that this function requires the MANDRILL_API_KEY constant to be defined
 * in order for it to work. The easiest place to define this is in wp-config.
 *
 * @since  0.0.1
 * @access public
 * @todo   Add support for attachments
 * @param  string $to
 * @param  string $subject
 * @param  string $message
 * @param  mixed $headers
 * @param  array $attachments
 * @return bool true if mail has been sent, false if it failed
 */
function wp_mail( $to, $subject, $message, $headers = '', $attachments = array() ) {
	// Return early if our API key hasn't been defined.
	if ( ! defined( 'MANDRILL_API_KEY' ) ) {
		return false;
	}

	// Compact the input, apply the filters, and extract them back out
	extract( apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) ) );

	// Get the site domain and get rid of www.
	$sitename = strtolower( parse_url( site_url(), PHP_URL_HOST ) );
	if ( 'www.' === substr( $sitename, 0, 4 ) ) {
		$sitename = substr( $sitename, 4 );
	}

	$from_email = 'wordpress@' . $sitename;

	$message_args = array(
		// Email
		'subject'                    => $subject,
		'to'                         => $to,
		'headers'                    => array(
			'Content-type'           => apply_filters( 'wp_mail_content_type', 'text/plain' ),
		),

		// Mandrill defaults
		'tags'                       => array(
			'user'                   => array(),
			'general'                => array(),
			'automatic'              => array(),
		),
		'from_name'                  => 'WordPress',
		'from_email'                 => $from_email,
		'template_name'              => '',
		'track_opens'                => null,
		'track_clicks'               => null,
		'url_strip_qs'               => false,
		'merge'                      => true,
		'global_merge_vars'          => array(),
		'merge_vars'                 => array(),
		'google_analytics_domains'   => array(),
		'google_analytics_campaign'  => array(),
		'meta_data'                  => array(),
		'important'                  => false,
		'inline_css'                 => null,
		'preserve_recipients'        => null,
		'view_content_link'          => null,
		'tracking_domain'            => null,
		'signing_domain'             => null,
		'return_path_domain'         => null,
		'subaccount'                 => null,
		'recipient_metadata'         => null,
	);

	$message_args = apply_filters( 'mandrill_wp_mail_pre_message_args', $message_args );

	// Make sure our to value is an array so we can manipulate it for the API.
	if ( ! is_array( $message_args['to'] ) ) {
		$message_args['to'] = explode( ',', $message_args['to'] );
	}

	 // Sneaky support for multiple to addresses.
	$processed_to = array();
	foreach ( (array) $message_args['to'] as $email ) {
		if ( is_array( $email ) ) {
			$processed_to[] = $email;
		} else {
			$processed_to[] = array( 'email' => $email );
		}
	}
	$message_args['to'] = $processed_to;

	// Set up message headers if we have any to send.
	if ( ! empty( $headers ) ) {
		$message_args = _mandrill_wp_mail_headers( $headers, $message_args );
	}

	if ( $message_args['headers']['Content-type'] === 'text/plain' ) {
		$message_args['text'] = $message;
	} else {
		$message_args['html'] = $message;
		$message_args['auto_text'] = true;
	}

	// Default filters we should still apply.
	$message_args['from_email'] = apply_filters( 'wp_mail_from', $message_args['from_email'] );
	$message_args['from_name']  = apply_filters( 'wp_mail_from_name', $message_args['from_name'] );

	// Allow user to override message args before they're sent to Mandrill.
	$message_args = apply_filters( 'mandrill_wp_mail_message_args', $message_args );

	$request_args = array(
		'body' => array(
			'message' => $message_args,
			'key'     => MANDRILL_API_KEY,
		)
	);

	$request_url = 'https://mandrillapp.com/api/1.0/messages/send.json';
	$response = wp_remote_post( $request_url, $request_args );
	if ( 200 !== wp_remote_retrieve_response_code( $response ) ) {
		return false;
	}

	return true;
}

/**
 * Handle email headers before they're sent to the Mandrill API.
 *
 * @since  0.0.2
 * @access private
 * @todo   Improve BCC handling
 * @param  mixed $headers
 * @param  array $message_args
 * @return array $message_args
 */
function _mandrill_wp_mail_headers( $headers, $message_args ) {
	if ( ! is_array( $message_args ) ) {
		return $message_args;
	}

	// Prepare the passed headers.
	if ( ! is_array( $headers ) ) {
		$headers = explode( "\n", str_replace( "\r\n", "\n", $headers ) );
	}

	// Bail if we don't have any headers to work with.
	if ( empty( $headers ) ) {
		return $message_args;
	}

	foreach ( (array) $headers as $header ) {

		if ( false === strpos( $header, ':' ) ) {
			continue;
		}

		// Explode them out
		list( $name, $content ) = explode( ':', trim( $header ), 2 );

		// Cleanup crew
		$name    = trim( $name );
		$content = trim( $content );

		switch ( strtolower( $name ) ) {

			case 'from':
				$from_email = trim( $content );

				if ( false !== strpos( $content, '<' ) ) {
					// So... making my life hard again?
					$from_name = substr( $content, 0, strpos( $content, '<' ) - 1 );
					$from_name = str_replace( '"', '', $from_name );
					$from_name = trim( $from_name );

					$from_email = substr( $content, strpos( $content, '<' ) + 1 );
					$from_email = str_replace( '>', '', $from_email );
					$from_email = trim( $from_email );

					$message_args['from_name'] = $from_name;
				}

				$message_args['from_email'] = $from_email;
			break;

			case 'cc':
				$cc           = explode( ',', $content );
				$processed_cc = array();
				foreach ( (array) $cc as $email ) {
					$processed_cc[] = array(
						'email' => trim( $email ),
						'type'  => 'cc',
					);
				}
				$message_args['to'] = array_merge( $message_args['to'], $processed_cc );
			break;

			case 'bcc':
				$bcc           = explode( ',', $content );
				$processed_bcc = array();
				foreach ( (array) $bcc as $email ) {
					$processed_bcc[] = array(
						'email' => trim( $email ),
						'type'  => 'bcc',
					);
				}
				$message_args['to'] = array_merge( $message_args['to'], $processed_bcc );
			break;

			case 'reply-to':
				$message_args['headers'][ trim( $name ) ] = trim( $content );
			break;

			case 'importance':
			case 'x-priority':
			case 'x-msmail-priority':
				if ( ! $message_args['important'] ) {
					$message_args['important'] = ( strpos( strtolower( $content ), 'high' ) !== false ) ? true : false;
				}
			break;

			case 'content-type':
				$message_args['headers']['Content-type'] = trim( $content );
			break;

			default:
				if ( 'x-' === substr( $name, 0, 2 ) ) {
					$message_args['headers'][ trim( $name ) ] = trim( $content );
				}
			break;
		}
	}
	return apply_filters( 'mandrill_wp_mail_headers', $message_args );
}