Description:
------------
I think is_callable() should check for existing methods instead of returning true all the time when the class uses overloading. Otherwise it becomes useless.

This is IMO particularly true for static methods checks, since __call is defined as non-static.



Reproduce code:
---------------
class A {
	public function __call($m, $a) {
	
	}
}

class B extends A {
	public static function foo() {
		echo 'foo';
	}
}

if (is_callable(array('A', 'foo'))) {
	call_user_func(array('A', 'foo'));
}

Expected result:
----------------
Outputs nothing.


Actual result:
--------------
Fatal error: Call to undefined method A::foo()