phpmailer stops suddenly in case of big attachments - php

Question

Problem
I have a script to send newsletters to my contacts. The script works fine, if I have no attachement (proven with 2,000 emails).
Now, if I use attachments, the script works fine too. But only by sending about 30 emails.
Test-Setup
group of 100 emails to be performed (loop).
attachments: 2 files (total 4,6 MB) --> the script terminates (but without error message) after 50 seconds and 34 emails sent. (~ 156 MB).
Test-Variations
changing in php.ini memory_limit from 100M to 500M --> has no effect. Still error after 34 emails.
putting a sleep(5) after each loop --> has no effect. Still error after 34 emails.
no attachments: all 100 emails are sent (about 30 seconds).
no attachements on 2000 emails: all 2000 emails are sent (about 6 minutes).
no effect of changing max_execution_time in php.ini.
Assumtions
Due to the behaviour I expect to have a memory-problem and not a time-problem.
But a test of the memory (memory_get_usage()) in each loop showed that the memory of the first loop is 1.1 MBand of the 34th loop 1.2 MB.
Question
Please find below my code, but I guess it sould be ok.
Does anybody has an idea what is causing the issue? Many thanks!
myMailer.class
class myMailer extends PHPMailer {
public function __construct(?bool $exceptions = true) {
$config = parse_ini_file('../../ini/config.ini', true);
parent::__construct($exceptions);
try {
// Language of Errors
$this->setLanguage('en', dirname(__FILE__) . '/../external/PHPMailer/language/');
// Server settings
$this->SMTPDebug = 0; // Enable verbose debug output
$this->isSMTP(); // Set mailer to use SMTP
$this->SMTPAuth = true; // Enable SMTP authentication
$this->SMTPSecure = 'ssl'; // Enable TLS encryption, `ssl` also accepted
$this->Port = 465; // TCP port to connect to
$this->Host = $config['smtp_server']['host']; // SMTP server
$this->Username = $config['smtp_server']['username']; // SMTP username
$this->Password = $config['smtp_server']['password']; // SMTP password
$this->CharSet ='UTF-8'; // Set Character Set
$this->isHTML(true); // Set email format to HTML
$this->setFrom("office#superman.com", "superman OFFICE");
} catch (Exception $e) {
// echo 'Message could not be sent. Mailer Error: ', $mail->ErrorInfo;
trigger_error("myMailer(): " . $this->ErrorInfo,E_USER_ERROR);
}
}
public function setBody(string $salutation, string $receiver, string $message) : void {
// Linebreak to <BR>
$message = nl2br($message);
// Create Body
$body = file_get_contents('../../ini/email_template.html');
$body = str_replace("{Receiver}", $receiver, $body);
$body = str_replace("{Salutation}", $salutation, $body);
$body = str_replace("{Message}", $message, $body);
$this->Body = $body;
}
}
send_emails.php
<?php
$groupID = $_POST['id'];
$subject = $_POST['Subject'];
$message = $_POST['Message'];
$attachments = (key_exists('Files', $_POST)) ? $_POST['Files'] : array();
$group = new Group($groupID);
// Prepare and get HTML
$htmlGenerator = HtmlGenerator::getInstance();
$htmlGenerator->setTitle("sending emails");
$header = $htmlGenerator->getWebbaseHtmlHeader();
$footer = $htmlGenerator->getWebbaseHtmlFooter();
echo $header;
?>
<div class="container">
<h1>Emailing</h1>
<h3>Group: <?php echo $group->getTitle(); ?></h3>
<h4>Number of members: <?php echo $group->getNumberOfMembers(); ?></h4>
<?php
$strScreenOutput = "
<table class='table table-sm table-hover table-responsive-md'>
<thead class='thead-dark'>
<th scope='col'>Nr.</th>
<th scope='col'>Date</th>
<th scope='col'>Company</th>
<th scope='col'>Lastname</th>
<th scope='col'>Firstname</th>
<th scope='col'>Email</th>
<th scope='col'>Newsletter</th>
<th scope='col'>Result</th>
</thead>
<tbody>";
$protocol = $strScreenOutput;
echo $strScreenOutput;
$i = 0;
$members = Contact::getAllOfGroup($groupID);
foreach ($members as $contact) {
$i++;
$datRun = date('d.m.Y (H:i:s)');
if ($contact->getNewsletter() === false) {
$result = "no sub.";
} elseif ($contact->getEmail() === "" || $contact->getEmail() === null) {
$result = "no email";
} else {
$return = $contact->sendEmail($subject, $message, $attachments);
$result = ($return===true) ? "ok" : $return;
}
// create feedback for browser
$strScreenOutput = "<tr>";
$strScreenOutput .= "<th scope='row'>".str_pad($i, 4 ,'0', STR_PAD_LEFT)."</th>";
$strScreenOutput .= "<td>{$datRun}</td>";
$strScreenOutput .= "<td>{$contact->getCompany()}</td>";
$strScreenOutput .= "<td>{$contact->getLastName()}</td>";
$strScreenOutput .= "<td>{$contact->getFirstName()}</td>";
$strScreenOutput .= "<td>{$contact->getEmail()}</td>";
$strScreenOutput .= "<td>".(($contact->getNewsletter()) ? "yes" : "no")."</td>";
$strScreenOutput .= "<td>{$result}</td>";
$strScreenOutput .= "</tr>";
echo str_pad($strScreenOutput,4096)."\n"; // Add some additional blanks to enable flushing (as some browsers suppress flushing)
// create internal protocol
$protocol .= $strScreenOutput . "\n";
// Send to browser
flush();
ob_flush();
// add some execution time
set_time_limit(30);
}
$strScreenOutput = "</tbody>
</table>";
$protocol .= $strScreenOutput;
echo $strScreenOutput;
?>
<h3>Emails successfully transmitted.</h3>
</div>
<?php
// send protocols
$protocol = "<h3>Group: {$group->getTitle()}</h3>".$protocol;
$protocol = "<div style='margin-top: 30px'>$protocol</div>";
$internal = new Contact(1);
$internal->sendEmail("PROTOCOL: ".$subject, $message . $protocol, $attachments);
echo $footer;
Contact::sendEmail()
public function sendEmail(string $subject, string $message, array $attachments = array()) {
$mail = new myMailer();
if ( is_null($this->getEmail() || $this->getEmail() == "") ) {
return false;
} else {
try {
// Compose Email
$mail->addAddress($this->getEmail(), $this->getFirstName() . " " . $this->getLastName());
$mail->Subject = $subject;
$mail->setBody($this->getSalutationText(), $this->getAddress(), $message);
foreach ($attachments as $file) {
$uploadPath = $_SERVER['DOCUMENT_ROOT'] . "/../../files/email_attachments/";
$file_url = $uploadPath.$file;
if (! is_dir($uploadPath)) { die("Folder \"$uploadPath\" does not exist.");}
if (! file_exists($file_url)) { die("File \"$file_url\" does not exist."); }
$mail->addAttachment($file_url);
}
$return = $mail->send();
// clean up
$mail->clearAddresses();
$mail->clearAttachments();
} catch (Exception $error) {
$return = $error->getMessage();
}
return $return;
}
unset($mail);
}

Answer 1

It does sound like a memory problem - PHPMailer isn't very efficient on memory when sending large attachments - try echoing what you get from memory_get_usage() inside your loop to confirm memory consumption.
Generally though, you're sending quite inefficiently because you're creating a new PHPMailer instance, reprocessing the same attachments, and opening a new SMTP connection for every message, all of which only need doing once. For how to send more efficiently, look at the mailing list example provided with PHPMailer, and the wiki doc on sending to lists.
A more efficient reuse of instance and connection may reduce your overall memory requirements.