Extension not installing on Mac, works on Windows

Question

I have written a safari extension which I'm able to install on Windows Safari, but it's not installing on a Mac Safari. On mac, when the link to the extension is clicked, executable text shows up (the initial bit is pasted here) -
xar! D}!? jz{_gw JqKt` H35$ Z8S1 wU2 0 \WCy. )1;L 51?k #c^ < "at* tcj* bZ6YhA x+XEsL H[c# m 2t &5{u<Z$ mfG# (Rt? :Lt%W 93in MP4% 3vBnV =-|7 DHz7O
The extension is available here http://snake.ims.uwm.edu/articlesearch/extensions.php . It was packaged on a Windows Safari (I don't have access to a Mac, but the bug was reported from two different sources).
Any idea why this might be happening?

Answer 1

Thanks. The following code worked for me (for others!)
<?php
header("Content-type: application/x-safari-extension");
header("Content-Disposition: attachment; filename=figsearch.safariextz");
readfile("figsearch.safariextz");
?>