I\'m adding an external class to a cake 3.0 app by putting it to /vendor/name folder and requiring it from a component like this:
require_once( $_SERVER[\'D
CakePHP 3.0 uses namespaces. So use proper namespace for your vendor class or if it's not using namespaces prefix the class name with backslash when using it.
E.g. $object = new \Test_Class();.
$object = new \Test_Class();