<?php function add_odd_numbers($x, $y) { assert('!(($x % 2) && ($y % 2))'); return ($x + $y); } $answer_one = add_odd_numbers(3, 5); $answer_two = add_odd_numbers(2, 4); echo "3 + 5 = $answer_one\n"; echo "2 + 4 = $answer_two\n"; ?>