Mine

function add_nd($number) {
		if (!is_numeric($number)) {
			return $number;
		}
		$suffix = '';
		$last_digit = substr($number,-1);
		if ($last_digit == 1) {
			$suffix = 'st';
		} elseif ($last_digit == 2) {
			$suffix = 'nd';
		} elseif ($last_digit == 3) {
			$suffix = 'nd';
		} else {
			$suffix = 'th';
		}
		return $number.$suffix;
	}