<?php

/**
 * @param int $a
 * @return bool
 */
function isEven($a) {
    return ($a % 2) === 0;
}

/**
 * TODO: Rely on isEven, but do not highlight bug.
 *
 * @param int $a
 * @return bool
 */
function isOdd($a) {
    return ($a % 2) === 1;
}