Adds a PDF invoice attachment to checkout emails.

pmpro-add-pdf-invoice-attachment.php

<?php
/*
Add a PDF attachement of the invoice to the checkout email. This code gist must be configured...

1) Download the DOMPDF library: https://github.com/dompdf/dompdf
	1.1) Save to wp-content/your-plugin/
2) Download the PHP SVG library: https://github.com/PhenX/php-svg-lib
	2.1) Save to dompdf/lib/
3) Download the PHP FONT library: https://github.com/PhenX/php-font-lib
	3.1) Save to dompdf/lib/

Upon checkout, will create a folder (...wp-content/invoices/[user_name]/ and add a PDF invoice. The content is the exact copy of the email.

*/

use Dompdf\Dompdf;

function my_init()
{
	include 'dompdf/autoload.inc.php';
	
	global $dompdf;
	
	$dompdf = new Dompdf();

}

add_action('init', 'my_init');

function my_pmpro_email_attachments($attachments, $email)
{
	global $dompdf;
	
	//make sure it's a checkout email (but not the admin one)
	if(strpos($email->template, "checkout_") !== false && strpos($email->template, "admin") === false)
	{
		//make sure attachments is an array
		if(is_array($attachments))
			$attachments = array();
			
		$dompdf->loadHtml($email->body);
		$dompdf->render();
		$output = $dompdf->output();
		
		$user_login = $email->data['user_login'];
		
		$upload_dir = wp_upload_dir();
		$user_dirname = $upload_dir['basedir'].'/invoices/'.$user_login;
		if (!file_exists( $user_dirname ))
		{
			wp_mkdir_p( $user_dirname );
		}
		
		$date = date("Y-m-d");
		
		$path = $user_dirname."/invoice-".$date.".pdf";
		
		file_put_contents($path, $output);
		
		//add our attachment
		$attachments[] = $path;
	}
	
	return $attachments;
}
add_filter('pmpro_email_attachments', 'my_pmpro_email_attachments', 10, 2);