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

Answer 1

function sortByLastName($a){
    $tmp = $a;
    foreach($tmp as $k => $v){
        $tmp[$k] = substr($v,strrpos($v, ' ')+1);
    }
    asort($tmp);
    $ret = array();
    foreach($tmp as $k => $v){
        $ret[$k] = $a[$k];
    }
    return $ret;
}

Maybe not the fastest way but it works. It works if they have middle names too.

This is faster than the accepted answer.

http://codepad.org/ogGibRpH