number-ordinal.php

<?php

function ordinal_suffix($n) {
  $j = $n % 10;
  $k = $n % 100;
  if (!($k >= 11 && $k <= 19)) {
    switch($j) {
      case 1:
        return "st";
      case 2:
        return "nd";
      case 3:
        return "rd";
    }
  }
  return "th";
}