Version 7.0.2 fixed 31 bugs, including six security vulnerabilities, in PHP 7, while version 5.6.17 fixed 14 bugs. PHP 5.5.31 closed five vulnerabilities in PHP 5.5, which is in security support mode until July 2016.
PHP 5.4 reached its end of life in October with 5.4.45 and is no longer maintained. Developers still on PHP 5.4 are strongly recommended to upgrade to a maintained version, to PHP 5.6 or PHP 7. Considering how many Web applications run PHP and how frequently they come under attack, using outdated versions makes it easier for attackers to exploit vulnerabilities.
