Description:
------------
When extends a class with FilterIterator, the valid ,current,key, next functions can't work, until you override your function with the following codes
public function valid() {
     $this->getInnerIterator()->valid();  
}

btw, my php works version is 5.2.6, I can't found this version in the select list , so I selected 5.2.9

Reproduce code:
---------------
error_reporting ( E_ALL | E_STRICT );
$array = array ('koala', 'kangaroo', 'wombat', 'wallaby', 'emu', 'NZ' => 'kiwi', 'kookaburra', 'platypus' );

class CullingIterator extends FilterIterator {
	
	public function __construct(Iterator $it) {
		parent::__construct ( $it );
	}
	
	function accept() {
		$ittmp = $this->getInnerIterator ();
		if ($ittmp->current () == 'koala') {
			return false;
		}
		return true;
	}
}

$cull = new CullingIterator ( new ArrayIterator ( $array ) );

try {
	while ( $cull->valid () ) {
 		echo $cull->current ();
		$cull->next ();
	}
} catch ( Exception $e ) {
	$e->getTraceAsString ();
}

Expected result:
----------------
print out the array result as following
kangaroowombatwallabyemukiwikookaburraplatypus


Actual result:
--------------
print nothing, becuase when we call $cull->valid() will return false

additional information , I've also tracked this problem by the following code, 

$cull = new CullingIterator ( new ArrayIterator ( $array ) );

$it = $cull->getInnerIterator();

var_dump( $it->valid() );

and the result is bool(true), it's very strange to get this while we $cull->valid() it return false(true)