Why PHP doesn't allow $class->property()

gistfile1.aw

<?php

class Test {
     public function foo() {
         echo 'I am happy and called';
     }
}

$test = new Test();
$test->foo = function() { echo 'dynamic'; };

$test->foo(); // WTF do I call? the closure named foo? or the function named foo? how would you write those rules?  Who wouldn't be angry with whatever was suggested? and what about the slowdown from the double hashtable lookup?