Create a random string of a given length in PHP

randomString.php

<?php

/**
 * Return a random string of a set number of characters.
 *
 * @param int $length  The number of characters for the resulting string
 * @param string $set  The set of characters to use for the random string
 * @param int $repeat  Number of times a given character may be repeated in the random string
 * @return string
 */
function randomString(
    $length,
    $set = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789',
    $repeat = 10
) {
    return substr(str_shuffle(str_repeat($set, $repeat)), 0, $length);
}