Switch to PHP 5.6 for compliance with Plesk itself.

Author: sibprogrammer

composer.json

@@ -10,7 +10,7 @@
     ],
     "minimum-stability": "dev",
     "require": {
-        "php": ">=5.5.0"
+        "php": ">=5.6.0"
     },
     "require-dev": {
         "phpunit/phpunit": "5.5.*",