Well maybe noone will ever use array_walk in Classes, but this should at least be documented:
_________SCRIPT_____________
class foo {
	var $files = array();
	
	// CONSTRUCTOR
	function foo() {
                // fill up the files array
		$this->files = $this->memberfunc_1();
		// do something with the array
                array_walk($this->files, "$this->memberfunc_2");
		// or "memberfunc_2" or "this->memberfunc_2"
	}
		
	// create a unique filename and clean up the real filename
	function memberfunc_2(&$c_arr) {
		// do some stuff ....
	}
} // end class

$bar = new foo();
____________END SCRIPT______________

This code leads to an Error Like :
Warning: Unable to call this->memberfunc_2() - function does not exist in .....