Description:
------------
When i try ${'_'.'POST'} in object __call i get: Notice: Undefined variable: _POST in ...

Test script:
---------------
<?php
	class A {
		public function __call($method, $args){
			var_dump($_POST, ${'_POST'}, ${'_'.'POST'}, '_POST' == '_'.'POST', $_POST == ${'_POST'});
		}
	}
	$class = new A();
	$class->test();

Expected result:
----------------
array(0) { } array(0) { } NULL bool(true) bool(true)