PHP mail with attachment, attachment file is noname - php

Question

I have the following code, which correctly sends an email with an attachment of the correct size, however the attachment comes in as 'noname' without an extension. If I rename the file manually after downloading it does not work. The file is an mp4 video.
<?php
$htmlbody = " Your Mail Contant Here.... You can use html tags here...";
$to = "blah#gmail.com"; //Recipient Email Address
$subject = "Test email with attachment"; //Email Subject
$headers = "From: test#mysite.com\r\nReply-To: test#mysite.com";
$random_hash = md5(date('r', time()));
$headers .= "\r\nContent-Type: multipart/mixed;
boundary=\"PHP-mixed-".$random_hash."\"";
// Set your file path here
$attachment = chunk_split(base64_encode(file_get_contents('test.mp4')));
//define the body of the message.
$message = "--PHP-mixed-$random_hash\r\n"."Content-Type: multipart/alternative;
boundary=\"PHP-alt-$random_hash\"\r\n\r\n";
$message .= "--PHP-alt-$random_hash\r\n"."Content-Type: text/plain;
charset=\"iso-8859-1\"\r\n"."Content-Transfer-Encoding: 7bit\r\n\r\n";
//Insert the html message.
$message .= $htmlbody;
$message .="\r\n\r\n--PHP-alt-$random_hash--\r\n\r\n";
//include attachment
$message .= "--PHP-mixed-$random_hash\r\n"."Content-Type: video/vnd.uvvu.mp4
name=\"testing.mp4\"\r\n"."Content-Transfer-Encoding:
base64\r\n"."Content-Disposition: attachment\r\n\r\n";
$message .= $attachment;
$message .= "/r/n--PHP-mixed-$random_hash--";
//send the email
$mail = mail( $to, $subject , $message, $headers );
echo $mail ? "Mail sent" : "Mail failed";
?>

Answer 1

Just modify this line, everything else stays the same:
$filename= "myvideo.mp4";
//include attachment
$message .= "--PHP-mixed-$random_hash\r\n"."Content-Type: video/vnd.uvvu.mp4
name=\"testing.mp4\"\r\n"."Content-Transfer-Encoding:
base64\r\n"."Content-Disposition: attachment; filename=\"".$filename."\"\r\n\r\n";