It would be very useful (at least for me) if the fonction foreach support references. For example the code :
<?
class Foo
{	var $Ok=false;
	function EchoOk()
	{	if ($this->Ok)
			echo "OK<br>\n";
		else
			echo "KO<br>\n";
	}
}

$Bar=array();
$Bar[]=new Foo;
foreach($Bar as $v)
	$v->SetOk();
foreach($Bar as $v)
	$v->EchoOk();
?>
will produce the output :
KO<br>

I know I can replace the first loop by :
foreach($Bar as $k => $v)
	$Bar[$k]->SetOk();
but, in this case, the $v is useless.

I suggest to accept the notation
foreach($Arr as &$RefVal)
and
foreach($Arr as $Key => &$RefVal)
in a future PHP release to make $RefVal a reference on each $Arr elements (and not a copy).