Send a WooCommerce Customer email from the Order Admin Actions

class-wc-kia-class-email.php

<?php
if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly

if ( ! class_exists( 'WC_KIA_Class_Email', false ) ) :

	/**
	 * A custom Order WooCommerce Email class
	 *
	 * @since 0.1
	 * @extends \WC_Email
	 */
	class WC_KIA_Class_Email extends WC_Email {


		/**
		 * Set email defaults
		 *
		 * @since 0.1
		 */
		public function __construct() {

			// set ID, this simply needs to be a unique name
			$this->id = 'wc_zlp_class';
			$this->customer_email = true;

			// this is the title in WooCommerce Email settings
			$this->title = __( 'Test Order Email', 'your-plugin-textdomain' );

			// this is the description in WooCommerce email settings
			$this->description = __( 'Test Notification emails are sent when a customer places an order switches to processing', 'your-plugin-textdomain' );

			// these are the default heading and subject lines that can be overridden using the settings
			$this->heading = __( 'Test Order Email', 'your-plugin-textdomain' );
			$this->subject = __( 'Test Order Email', 'your-plugin-textdomain' );

			// these define the locations of the templates that this email should use, we'll just use the new order template since this email is similar
			$this->template_html  = 'emails/customer-processing-order.php';
			$this->template_plain = 'emails/plain/customer-processing-order.php';
			$this->placeholders   = array(
				'{order_date}'   => '',
				'{order_number}' => '',
			);

			// Triggers for this email.
			//add_action( 'woocommerce_order_status_cancelled_to_processing_notification', array( $this, 'trigger' ), 10, 2 );
			//add_action( 'woocommerce_order_status_failed_to_processing_notification', array( $this, 'trigger' ), 10, 2 );
			//add_action( 'woocommerce_order_status_on-hold_to_processing_notification', array( $this, 'trigger' ), 10, 2 );
			//add_action( 'woocommerce_order_status_pending_to_processing_notification', array( $this, 'trigger' ), 10, 2 );

			// Manually send via admin order actions.
			add_action( 'woocommerce_order_action_kia_email_class_detail_action', array( $this, 'trigger' ) );

			// Call parent constructor to load any other defaults not explicity defined here
			parent::__construct();

		}


		/**
		 * Get email subject.
		 *
		 * @since  3.1.0
		 * @return string
		 */
		public function get_default_subject() {
			return __( 'Your {site_title} order is totally happening!', 'your-plugin-textdomain' );
		}

		/**
		 * Get email heading.
		 *
		 * @since  3.1.0
		 * @return string
		 */
		public function get_default_heading() {
			return __( 'You deserve all the tacos', 'your-plugin-textdomain' );
		}

		/**
		 * Trigger the sending of this email.
		 *
		 * @param int            $order_id The order ID.
		 * @param WC_Order|false $order Order object.
		 */
		public function trigger( $order_id, $order = false ) {
			$this->setup_locale();

			if ( $order_id && ! is_a( $order, 'WC_Order' ) ) {
				$order = wc_get_order( $order_id );
			}

			if ( is_a( $order, 'WC_Order' ) ) {
				$this->object                         = $order;
				$this->recipient                      = $this->object->get_billing_email();
				$this->placeholders['{order_date}']   = wc_format_datetime( $this->object->get_date_created() );
				$this->placeholders['{order_number}'] = $this->object->get_order_number();
			}

			if ( $this->is_enabled() && $this->get_recipient() ) {
				$success = $this->send( $this->get_recipient(), $this->get_subject(), $this->get_content(), $this->get_headers(), $this->get_attachments() );

				if( $success ) {
					// ADD THE ORDER NOTE
					$message = sprintf( __( 'Class detail for "%s" is sent.', 'zlp_class' ), $order->get_meta( 'class_name', true ) );

					$order->add_order_note( $message );

					// ADD THE FLAG SO THIS ACTION WON'T BE SHOWN AGAIN (I don't really now if that's good... you might need to resend it)
				//	$order->update_meta_data( '_wc_order_class_detail_sent', 'yes' );
					$order->save();
				}
			}

			$this->restore_locale();
		}

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

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

		/**
		 * Default content to show below main email content.
		 *
		 * @since 3.7.0
		 * @return string
		 */
		public function get_default_additional_content() {
			return __( 'Thanks for using {site_address}!', 'your-plugin-textdomain' );
		}

	} // end \WC_KIA_Class_Email class

	endif;

return new WC_KIA_Class_Email();

wc-example-manual-email.php

<?php
/*
 * Plugin Name: Example Manual WooCommerce Email
 * Plugin URI: https://gist.github.com/helgatheviking/cf3483038995dff909d1229b3e844ce5
 * Donation URL: https://paypal.me/helgatheviking
 * Description: Send a customer email from the Order Admin Actions.
 * Version: 1.0
 * Author: Kathy Darling
 * Author URI: http://kathyisawesome.com
 * Requires at least: 5.0.0
 * WC requires at least: 4.0.0    
 * Tested up to: 5.3.0
 * WC tested up to: 4.1.0   
 *
 * Text Domain: wc_name_your_price
 * Domain Path: /languages/
 *
 * Copyright: © 2012 Kathy Darling.
 * License: GNU General Public License v3.0
 * License URI: http://www.gnu.org/licenses/gpl-3.0.html
 *
 */
defined( 'ABSPATH' ) || exit;


/**
 *  Add a custom email to the list of emails WooCommerce should load
 *
 * @since 0.1
 * @param array $email_classes available email classes
 * @return array filtered available email classes
 */
function kia_add_order_woocommerce_email( $email_classes ) {

	// add the email class to the list of email classes that WooCommerce loads
	$email_classes['WC_ZLP_Class_Email'] = require_once( 'class-wc-kia-class-email.php' );

	return $email_classes;

}
add_filter( 'woocommerce_email_classes', 'kia_add_order_woocommerce_email' );

/**
 *  Add a custom email to the list of emails WooCommerce should load
 *
 * @since 0.1
 * @param array $email_classes available email classes
 * @return array filtered available email classes
 */
function kia_wc_add_order_meta_box_action( $actions ) {
	global $theorder;
	
	// ADD "Email class details" CUSTOM ACTION
	$actions['kia_email_class_detail_action'] = __( 'Email class details', 'kia_class' );
	
	return $actions;
}
add_action( 'woocommerce_order_actions', 'kia_wc_add_order_meta_box_action' );


/**
 * Register 'woocommerce_order_action_kia_email_class_detail_action' as an email trigger
 * 
 * @param array $actions actions that trigger emails
 * @return array
 * 
 */
function kia_custom_woocommerce_email_actions( $actions ){
	$actions[] = 'woocommerce_order_action_kia_email_class_detail_action';
	return $actions;
}
add_filter( 'woocommerce_email_actions', 'kia_custom_woocommerce_email_actions' );



function action_test() {
	error_log('action does run');
}
add_action( 'woocommerce_order_action_kia_email_class_detail_action', 'action_test' );