As of PHP 5, you can easily modify array's elements by preceding $value with &. This will assign reference instead of copying the value.
<?php
$arr = array(1, 2, 3, 4);
foreach ($arr as &$value) {
$value = $value * 2;
}
// $arr is now array(2, 4, 6, 8)
unset($value); // break the reference with the last element
?>

Tratto dal manuale di php
http://us.php.net/manual/en/control-...es.foreach.php