We are using ::class which is php 5.5

Nyholm · Nyholm · commit cf2ab9d4474b · 2016-06-27T08:43:53.000+02:00
diff --git a/composer.json b/composer.json
@@ -11,7 +11,7 @@
         }
     ],
     "require": {
-        "php": "^5.4 || ^7.0"
+        "php": "^5.5|^7.0"
     },
     "require-dev": {
         "php-http/httplug": "^1.0",
