Description:
------------
Using a reference to build an array, later causes foreach to fail when reusing the reference variable name.

The bug is solved by adding unset( $element); before block B, but this shouldn't be necessary.

Reproduce code:
---------------
// Block A - Build the Array
$a = array( 2 => array( "value" => "a" ), 
			4 => array( "value" => "b" ),
			6 => array( "value" => "c" ) );
			
$b = array( "orange", "blue", "green" );

foreach( $a as $id => &$element ){
	$extra = array();
	
	foreach( $b as $color )
		array_push( $extra, $color );
		
	$element += array( 'extra' => $extra );
}

// Block B - Iterate through
foreach( $a as $element )
	echo $element["value"].' ';


Expected result:
----------------
a b c

Actual result:
--------------
a b b