Is there a way to prevent that ReflectionClass interprets the class?

class A
{
    public function x($a) { }
}

class B
{
    public function x() { }
}

new ReflectionClass('B');

when using ReflectionClass, it interprets the whole class. Actually I would only use its getConstructor() but it fails (incompatible methods). I dont care if class is declared bad, I just want the getConstructor, how to eliminate that?