MPDF E-mail Attachment Sends Blank PDF - php

Question

I have successfully generated a PDF using mpdf, which I have verified by downloading the PDF. However, when I send the PDF as an e-mail attachment I receive a blank PDF with an "Out of Memory" error by Adobe Reader. Below is my code:
<?php
include("MPDF57/mpdf.php");
ob_start();
include "Receipt_Template_2.php";
$template = ob_get_contents();
ob_end_clean();
$mpdf=new mPDF('','A4','','',32,25,27,25,16,13,'L');
mpdf->WriteHTML($template);
$content = $mpdf->Output($template, 'S');
$content = chunk_split(base64_encode($content));
$mailto = 'sample#sample.com';
$from_name = 'KIREA';
$from_mail = 'NoReply#kirea.ca';
$uid = md5(uniqid(time()));
$subject = 'KIREA Donation Receipt';
$message = "Thank you for your donation!\n\nAttached is the receipt concerning the donation. If you have any questions, please e-mail us at receipts#kirea.ca";;
$filename = $pdfName;
$header = "From: ".$from_name." <".$from_mail.">\n";
$header .= "MIME-Version: 1.0\n";
$header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"\n";
$header .= "This is a multi-part message in MIME format.\n";
$header .= "--".$uid."\r\n";
$header .= "Content-type:text/plain; charset=iso-8859-1\n";
$header .= "Content-Transfer-Encoding: 7bit\n";
$header .= $message."\n\r\n";
$header .= "--".$uid."\n";
$header .= "Content-Type: application/pdf; name=\"".$filename."\"\n";
$header .= "Content-Transfer-Encoding: base64\n";
$header .= "Content-Disposition: attachment; filename=\"".$filename."\"\n\n";
$header .= $content."\n\n";
$header .= "--".$uid."--";
$is_sent = #mail($mailto, $subject, "", $header);
$mpdf->Output();
exit;
?>
Are there any ideas as to why the PDF is ending up blank after being sent as an e-mail attachment? Thank you.

Answer 1

mpdf->WriteHTML($template);
$content = $mpdf->Output($template, 'S');
You are wrong at here you are not taking the object on which your data is written
please replace below code with above to get correct result.
$pdfdata=mpdf->WriteHTML($template);
$content = $mpdf->Output('' , 'S');
use $content in your email

Answer 2

If you can use swiftmailer, you can attach a MPDF generated PDF to the email, quite easily as follows:
<?php
require_once $swift_mailer_path.'swift_required.php';
$transporter = Swift_SmtpTransport::newInstance($smtp_host, $smtp_port, $smtp_protocol)
->setUsername($smtp_username')
->setPassword($smtp_password');
$mailer = Swift_Mailer::newInstance($transporter);
$message = Swift_Message::newInstance('Email Subject')
->setFrom(array($from_email => $from_name))
->setTo($to_email)
->setBody($email_body);
$attachment = Swift_Attachment::newInstance($mpdf->Output($pdf_path, "S"), $pdf_file_name, 'application/pdf');
$message->attach($attachment);
$message->setContentType("text/html");
$result = $mailer->send($message);
?>
Here is the Reference.