[Sorry, Grammar Error.]When trying to get [an] element of reference inside an 
array, php always returns a 
copy of that variable being referred. See the comment of Test Script.

see blow:
<?php
$Item = array ('foo' => 'bar');
$Array = array (&$Item);
$rItem = & $Array[0]; 
$rItem['foo'] = 'foobar';
echo $Item['foo'];

OK. it's wired though.

Wired, still problemetic.
Compare with those two scripts:
<?php
	$ArrayMeta = array('a'=>1, 'b'=>array ('bb' => 2));
	$mPendingStack = array (&$ArrayMeta); 

	$mCurrArray = null; //Reference to current array.
	while (count($mPendingStack) != 0) {
		$mCurrArray = &$mPendingStack[count($mPendingStack)-1]; 
		unset($mPendingStack[count($mPendingStack)-1]);
		reset($mCurrArray);
		for ($i = 0; $i < count($mCurrArray); ++$i) {
			if (is_array($mCurrArray[key($mCurrArray)])) {
				$mPendingStack[count($mPendingStack)] = &$mCurrArray[key($mCurrArray)];
			}
			else {
				$mCurrArray[key($mCurrArray)] = null;
			}
			next($mCurrArray);
		}
	}
	
	var_dump($ArrayMeta);
?>
and
<?php


	$ArrayMeta = array('a'=>1, 'b'=>array ('bb' => 2));
	$mPendingStack = array (&$ArrayMeta); 

	$mCurrArray = null; //Reference to current array.
	while (count($mPendingStack) != 0) {
		$mCurrArray = &$mPendingStack[count($mPendingStack)-1]; 
		unset($mPendingStack[count($mPendingStack)-1]);
		foreach ($mCurrArray as &$mValue) {
			if (is_array($mValue)) {
				$mPendingStack[count($mPendingStack)] = &$mValue;
			}
			else {
				$mValue = null;
			}
		}
	}

	var_dump($ArrayMeta);
?>
Array elements of references can be found via both two ouputs, though those outputs were different. But the expected result should contains no reference, since I var_dump-
ed $ArrayMeta, which should be no reference inside it.

I think it is little bit buggy.

Those are tested under PHP 5.3.8 and PHP 5.3.5.

<?php
	$ArrayMeta = array('a'=>1, 'b'=>array ('bb' => 2));
	var_dump($ArrayMeta);
	$mPendingStack = array (&$ArrayMeta); 

	$mCurrArray = null; //Reference to current array.
	while (count($mPendingStack) != 0) {
		$mCurrArray = &$mPendingStack[count($mPendingStack)-1];
		unset($mPendingStack[count($mPendingStack)-1]);
		foreach ($mCurrArray as &$mValue) {
			if (is_array($mValue)) {
				$mPendingStack[count($mPendingStack)] = $mValue; //If I removed & before $mValue...
			}
			else {
				$mValue = null;
			}
		}
	}
	
	var_dump($ArrayMeta);

And still, PHP Manual shows me that the & symbol in foreach clause will produce reference. But this is also problemetic in this script. Only $ArrayMeta['a'] turned to 
null.