Among many fixes since 5.5.15, the following security issues were fixed:
CVE-2014-8142
CVE-2014-3710
CVE-2014-3669
CVE-2014-3670
CVE-2014-3668
CVE-2014-3538
CVE-2014-3587
CVE-2014-2497
CVE-2014-5120
CVE-2014-3597
For more details please see the upstream changelog:
http://php.net/ChangeLog-5.php
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>