PHP 5.3.7 contained a serious error in the way that it handled certain inputs to the crypt() function. The group warned users on Monday not to upgrade to that release and to wait until the bug could be fixed. On Tuesday the group released a new version of the language, PHP 53.8, which fixes the crypt(function) problem and rolls back a function introduced in 5.7 that was causing some SSL sessions to hang. The PHP Group recommended that all users upgrade to 5.8 as soon as possible. The older 5.2 chain is no longer supported.
Source: https://threatpost.com/php-538-released-fixes-crypto-bug-082411/75576/