Pass the arguments by reference. http://no.php.net/manual/en/language.references.php
<?php
// Example
$arr1 = array("one", "two", "three");
$arr2 = array(1, 2, 3);
arr ( &$arr1, &$arr2 );
for($i=0;$i<3;$i++)
echo "$i: $arr1[$i], $arr2[$i]<br>";
function arr ( $arr1, $arr2 ) {
$arr1[2] = "test";
$arr2[0] = "10";
$arr2[1] = "100";
}