Just a friendly reminder that PHP5.5 will stop receiving security support after the 10 July (17 Days at the time of writing).
It is advisable to upgrade to PHP 5.6 or PHP 7.0.
I would recommend you jump directly to 7.0 but it should be noted the support for PHP 5.6 has been extended to provide active support for an additional four moves and security fixes for additional 2 years. You can read more about the extended support of 5.6 in the PHP 5 Support Timeline RFC
Written By Simon Bennett (find me on Google+)