Description:
------------
debug_backtrace() crashes apache by using call_user_func.


Reproduce code:
---------------
<?php
	
	$class = new Test;
	$class->callMethod("execute");

class Test {
	function backtrace(){
		return debug_backtrace();
	}
	
	function display($dummy,$bk){
		print_r($bk);
	}
	
	function display2($bk){
		print_r($bk);
	}
	
	function callMethod($methodname){
		$ret = call_user_func(array($this,$methodname));
		
		return $ret;
	}
	
	function execute(){
		//CRASH!
		$this->display("dummy",$this->backtrace());

		//this works fine
//		$this->display("dummy",debug_backtrace());
		//this works fine too (only one arg)
//		$this->display2($this->backtrace());
	}
}


Expected result:
----------------
crash apache server

Actual result:
--------------
print backtrace normally