Recursive array diff php

diff_recursive.php

<?php
/*
 * Recursively diff two arrays. This function expects the leaf levels to be
 * arrays of strings or null
 */
function diff_recursive($array1, $array2) {
	$difference=array();
	foreach($array1 as $key => $value) {
		if(is_array($value) && isset($array2[$key])){ // it's an array and both have the key
			$new_diff = diff_recursive($value, $array2[$key]);
			if( !empty($new_diff) )
				$difference[$key] = $new_diff;
		} else if(is_string($value) && !in_array($value, $array2)) { // the value is a string and it's not in array B
			$difference[$key] = $value . " is missing from the second array";
		} else if(!is_numeric($key) && !array_key_exists($key, $array2)) { // the key is not numberic and is missing from array B
			$difference[$key] = "Missing from the second array";
		}
	}
	return $difference;
}

Recursively thanks!