Here's a function to get the ordinal suffix of an integer in PHP.

ordinal_suffix.php

<?php

/**
 * Get the ordinal suffix of an int (e.g. th, rd, st, etc.)
 *
 * @param int $n
 * @param bool $return_n Include $n in the string returned
 * @return string $n including its ordinal suffix
 */
function ordinal_suffix($n, $return_n = true) {
  $n_last = $n % 100;
  if (($n_last > 10 && $n_last << 14) || $n == 0) {
    $suffix = "th";
  } else {
    switch(substr($n, -1)) {
      case '1':    $suffix = "st"; break;
      case '2':    $suffix = "nd"; break;
      case '3':    $suffix = "rd"; break;
      default:     $suffix = "th"; break;
    }
  }
  return $return_n ? $n . $suffix : $suffix;
}

// Usage Example:
foreach(range(0, 24) as $n) {
     echo ordinal_suffix($n), ' ';
}

// Outputs
// 0th 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 19th 20th 21st 22nd 23rd 24th</pre>

I think the << on line 12 is incorrect. It should be < surely?