Write a PHP function to sort subnets

<?php
function sort_subnets ($x, $y) {
    $x_arr = explode('.', $x);
    $y_arr = explode('.', $y);
    foreach (range(0,3) as $i) {
        if ( $x_arr[$i] < $y_arr[$i] ) {
            return -1;
        }
        elseif ( $x_arr[$i] > $y_arr[$i] ) {
            return 1;
        }
    }
    return -1;
}

$subnet_list = 
array('192.169.12',
'192.167.11',
'192.169.14',
'192.168.13',
'192.167.12',
'122.169.15',
'192.167.16'
);
usort($subnet_list, 'sort_subnets');
print_r($subnet_list);
?>

Sample Output:

Array                                                       
(                                                           
    [0] => 122.169.15                                       
    [1] => 192.167.11                                       
    [2] => 192.167.12                                       
    [3] => 192.167.16                                       
    [4] => 192.168.13                                       
    [5] => 192.169.12                                       
    [6] => 192.169.14                                       
)