Post data to url using AppleScript
While I cannot throughly test your issue, because I don't have access to your site, nonetheless, the following line of code is malformed:

set theURL to "http://mysite/testing.php?email=email&amp;productKey=productKey"


It should be in the form of:

set theURL to "http://mysite/testing.php?email=" &amp; email &amp; "&amp;productKey=" &amp; productKey