Description:
------------
I cannot expect this to come any time soon, maybe for 6CVS.

For isset() and unset() we now have __isset and __unset overload methods. We need another magic method for method_exists, e.g., __ismethod (or a similiar name, __iscallable, etc).

Reproduce code:
---------------
<?php

class Foo {
   public function __call( $method, $args ) {
     // some magic with $methods
   }
   
   public function __ismethod( $method ) {
      // returns true or false if $method is a
      // valid method
   }
}

?>