Last week I was trying to figure out how to get a 28 character md5. An application I was trying to generate passwords required what looked to be a 28 char hash.

First off I tried

echo base64_encode(md5($password))

This returned way too many characters. After doing some research I found out it needs to be the binary out put of an md5. PHP 5+ has this option.

To get the md5 binary format in php add TRUE to the md5() function.

echo base64_encode(md5($password, true))

This also works with sha1(base64)

echo base64_encode(sha1($password, true))

Links
http://www.insidepro.com/hashes.php?lang=eng
http://www.caucho.com/resin/admin/security-overview.xtp