<?php

/*
 * Returns true with a given percentage.
 *
 * @param  int     $prob Probability for true in percent.
 * 
 * @return boolean
 */
function rand_bool($prob = 50) {
    if ($prob < 0 or $prob > 100) {
        throw new InvalidArgumentException('The value for the probability '.
          ' must be in a range from 0 to 100.');
    } else if (!is_int($prob)) {
        throw new InvalidArgumentException('rand_bool only accepts integers.');
    }

    $rand = rand(1, 100);

    return $rand <= $prob;
}