向PHP邮件添加附件

我正在尝试备份我的数据库，并通过电子邮件将zip文件发送给我。以下代码运行良好，只是没有附加zip。邮件和一切都很好，创建了zip文件，但我无法附加它。

$today = date("d/m/Y");
$to      = 'Chris P <chris@*****.co.uk>';
$subject = 'Back Up File - '.$today;
$headers = 'From: Backup <backup@******.co.uk>' . "'r'n" .
$headers.= 'Reply-To: ****** (Chris) <chris@******.co.uk>' . "'r'n" .
$headers.= "X-Mailer: PHP/" . phpversion()."'r'n";
$headers.= "MIME-Version: 1.0" . "'r'n";
$headers.= "Content-type: text/html; charset=iso-8859-1 'r'n";
$random_hash = md5(date('r', time()));
$attachment = chunk_split(base64_encode(file_get_contents($fileName)));
ob_start(); //Turn on output buffering

$message2  = "<font face='verdana' size='-2'>Hey Chris,<p>";
$message2 .= "Here is the back up of the database, taken on the <strong>$today.</strong>'n'n"; 
$message2 .= "<p>The archive has the name of:  <strong>$fileName</strong> and it's file-size is <strong>$fileSize.</strong>'n'n"; 
$message2 .= "Please find the file attatched.'n'n";
$message2 .= "<p>****** BackUp Generator ";
$message2 .= "--PHP-mixed- $random_hash;";
$message2 .= "Content-Type: application/zip; name='"$filename'""; 
$message2 .= "Content-Transfer-Encoding: base64"; 
$message2 .= "Content-Disposition: attachment";
$message2 .= $attachment;
$message2 .= "--PHP-mixed-<?php echo $random_hash; ?>--";