Description:
------------
Function is_callable will not handle private/public well from within a class.


Reproduce code:
---------------
<?php
class X {
	private function getXX($value) {
		return "XX $value";
	}
	
	function testXX() {
		echo (is_callable(array($this, 'getXX')) ? $this->getXX("test") : "Can't call getXX within " . __CLASS__) . "\n";
	}
}

class Y extends X {
	function testXX() {
		echo (is_callable(array($this, 'getXX')) ? $this->getXX("test") : "Can't call getXX within " . __CLASS__) . "\n";
	}
}
	
$x = new X;
echo (is_callable($x, 'getXX') ? $x->getXX("test") : "Can't call getXX outside for " . get_class($x)) . "\n";
$x->testXX();

$y = new y;
echo (is_callable($y, 'getXX') ? $y->getXX("test") : "Can't call getXX outside for " . get_class($y)) . "\n";	
$y->testXX();
?>

Expected result:
----------------
Can't call getXX outside for X
XX test
Can't call getXX outside for Y
Can't call getXX within Y

Actual result:
--------------
Can't call getXX outside for X
XX test
Can't call getXX outside for Y
<br />
<b>Fatal error</b>:  Call to private method X::getXX() from context 'Y' in <b>\\Seabert\webroot\ontwikkeling\quickbuild\test.php</b> on line <b>76</b><br />