How to sort an array of names by surname preserving the keys

Question

I have an array as follows:

Array(
    [27] => 'Sarah Green',
    [29] => 'Adam Brown',
    [68] => 'Fred Able'
);

I'd like to sort it by surname and preserve the keys:

Array(
    [68] => 'Fred Able'
    [29] => 'Adam Brown',
    [27] => 'Sarah Green'
);

Some names may have more than two first names, but it's always the very last name I want to sort on.

What would be the best way to do this in PHP?

Answer 1

You can use the uasort function, which allows you to specify a custom sorting method while also preserving keys:

<?php
// A function to sort by last name.
function lastNameSort($a, $b) {
    $aLast = end(explode(' ', $a));
    $bLast = end(explode(' ', $b));

    return strcasecmp($aLast, $bLast);
}

// The array of data.
$array = array(
    27 => 'Sarah Green',
    29 => 'Adam Brown',
    68 => 'Fred Able'
);

// Perform the sort:
uasort($array, 'lastNameSort');

// Print the result:
print_r($array);
?>

Here's a demo.