PHP 5.3.7 release has a major bug in MD5 crypt
bugs.php.net
bugs.php.net
Also, I just checked, there don't seem to be PHP unit tests for crypt(), in their tests directory. (http://svn.php.net/viewvc/php/php-src/branches/PHP_5_3/tests...).
http://svn.php.net/viewvc/php/php-src/branches/PHP_5_4/ext/s...