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

Probably something similar to this (have not tested)

function sortSurname($a,$b){
  $sur_a = array_pop(explode(' ',$a));
  $sur_b = array_pop(explode(' ',$b));
  return $sur_a < $sur_b;
}

usort($array, 'sortSurname')