A very easy way to handle attachments is just using munpack, with a subdirectory called attachments chmod it to 777 and then use the following bit of code (with mpack installed) on the MIME encoded body:

<?php
//email MIME body in $input
file_put_contents("attachments/body.eml",$input);
$command = "munpack -C attachments -fq body.eml";
exec($command,$output);
if($output[0]!='Did not find anything to unpack from body.eml') {
    foreach ($output as $attach) {
        $pieces = explode(" ", $attach);
        $part = $pieces[0];
        echo "<a href=\"attachments/$part\">$part</a><br>";
        }
    }
?>