PHPMailer 2 files same filesize are not sending both - php

Question

It just so happens we have two files that are the exact same size that we some times try to send together. We can send anything else we want with these files but as soon as we include both of them it only sends the first one. I'll include my phpmailer code just to be safe but its worked thus far.
$mail = new PHPMailer(true);
$mail->IsSendMail();
$mail->SetFrom($from_addy, $from_name);
foreach(explode(',',$to) as $address1){
foreach(explode(';',$address1) as $address2){
if($address2 != ''){
$mail->AddAddress($address2);
}
}
}
$mail->WordWrap = 70;
$mail->IsHTML(true);
$mail->Subject = $subject;
$mail->Body = $css.$message;
$mail->AltBody = nl2br($message);
$mail->MsgHTML($css.$message);
if(is_array($attachments)){
foreach($attachments as $attachment){
$file = file_get_contents($attachment['tmp_name']);
$mail->AddStringAttachment($file,$attachment['name']);
// I have put checks here and both attachments do make it this far.
}
}

Answer 1

You're not checking the return value from addStringAttachment so you don't know if it's working or not. PHPMailer doesn't throw exceptions for everything, and while you've requested them, you're not catching them anyway. Why read the file and use addStringAttachment - why not read the attachment directly from the file with addAttachment? String attachments are more useful when you need to attach the results of a remote API call, PDF generation etc. Like this:
if (!$mail->addAttachment($attachment['tmp_name'], $attachment['name'])) {
echo "Failed to attach ".$attachment['tmp_name'];
}
Why are you using isSendmail()? It's unlikely you need that.
You've not presented any evidence that it's got anything to do with the file size - it's not as if attachments are indexed by their size value or anything.
You're setting AltBody before calling msgHTML(), which overwrites AltBody. Calling nl2br() on AltBody contents is pointless because AltBody will usually be presented as plain text, so <br> tags will show up.
It looks like your $attachment array may be sourced from $_FILES, in which case it looks you are handling file uploads unsafely. read the PHP docs on that, and look at the "send file upload" example provided with PHPMailer.
Overall, it looks like you've based your code on a very old PHPMailer example, so make sure you're using the latest version, and look at the examples provided with it.