Are you sure the assignment to $result is correct as self::findFirst(array("i..., 'lifetime' => 1200))) (which targets Phalcon\Mvc\Model::findFirst()) seems to always return null.
This check looks for function or method calls that always return null and whose
return value is assigned to a variable.
Methods can only be called on objects. This check looks for methods being called on variables that have been inferred to never be objects.