Surname Sort

surnamesort.php

<?php
usort($array, function($a, $b) {
    // explode name a by spaces
    $parts_a = explode(' ', $a);
    // remove the last name from the end of the array
    $last_a  = array_pop($parts_a);
    // and shove it on the front
    array_unshift($parts_a, $last_a);
    // then re-implode into a string
    $a = implode(' ', $parts_a);
    // repeat the process for name b
    $parts_b = explode(' ', $b);
    $last_b  = array_pop($parts_b);
    array_unshift($parts_b, $last_b);
    $b = implode(' ', $parts_b);
    // perform a case insensitive string comparison
    return strcasecmp($a, $b);
});