Actualizando una Debian 7 me encuentro con este mensaje de fin del soporte de seguridad de PHP, por lo que es conveniente migrar a Debian 8.
php5 (5.4.45-0+deb7u2) wheezy-security; urgency=medium
* PHP 5.4 has reached end-of-life on 14 Sep 2015 and as a result there
will be no more new upstream releases. The security support of PHP
5.4 in Debian will be best effort only and you are strongly advised
to upgrade to latest stable Debian release that includes PHP 5.6 that
will reach end of security support on 28 Aug 2017.— Ondřej Surý <ondrej@debian.org> Sun, 04 Oct 2015 17:05:37 +0200