PHP - Generator of random string

file.php

<?php

    /**
     * Generates the random string specified length
     * @param int $length
     *
     * @return string
     */
    protected function getRandomString($length)
    {
        $salt = array_merge(range('a', 'z'), range(0, 9));
        $maxIndex = count($salt) - 1;

        $result = '';
        for ($i = 0; $i < $length; $i++) {
            $index = mt_rand(0, $maxIndex);
            $result .= $salt[$index];
        }

        return $result;
    }