Registering custom emails for WooCommerce

CustomOrderEmail.php

<?php


class CustomOrderEmail extends \WC_Email {


	// This is a just a simple example. See \WC_Email and child classes for more examples
	public function __construct() {
		$this->id             = 'custom_order_email';
		$this->title          = 'Custom Order Email';
		$this->description    = 'A custom order email that does …';
		$this->template_html  = 'path/to/html-template.php';
		$this->template_plain = 'path/to/plain-template.php';
		//$this->recipient      = 'someone@example.com';
		$this->customer_email = true;
		parent::__construct();
		$this->manual = true;
	}


	/**
	 * Trigger the sending of this email.
	 *
	 * @param int $order_id The order ID.
	 */
	public function trigger( $order_id ) {
		$order = wc_get_order( $order_id );

		if ( ! is_a( $order, 'WC_Order' ) ) {
			return;
		}

		$this->object    = $order;
		$this->recipient = $order->get_billing_email();

		if ( $this->is_enabled() && $this->get_recipient() ) {
			$this->setup_locale();
			$this->send(
				$this->get_recipient(),
				$this->get_subject(),
				$this->get_content(),
				$this->get_headers(),
				$this->get_attachments()
			);
			$this->restore_locale();
		}
	}


	/**
	 * @return string
	 */
	public function get_content_html() {
		return wc_get_template_html(
			$this->template_html, array(
				'order'         => $this->object,
				'email_heading' => $this->get_heading(),
				'sent_to_admin' => false,
				'plain_text'    => false,
				'email'         => $this,
			)
		);
	}


	/**
	 * @return string
	 */
	public function get_content_plain() {
		return wc_get_template_html(
			$this->template_plain, array(
				'order'         => $this->object,
				'email_heading' => $this->get_heading(),
				'sent_to_admin' => false,
				'plain_text'    => true,
				'email'         => $this,
			)
		);
	}


}

html-template.php

<?php 

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

do_action( 'woocommerce_email_header', $email_heading, $email );
?>

<p>Write your HTML in here</p>

<?php
do_action( 'woocommerce_email_footer', $email );

registration.php

<?php 

// need to include this otherwise the WC_Email class can't be extended
include_once wc()->plugin_path() . '/includes/emails/class-wc-email.php';

add_filter( 'woocommerce_email_classes', function ( $registered_emails ) {
	$registered_emails['Custom_Order_Email']    = new CustomOrderEmail();

	return $registered_emails;
} );