Random password generator (from Prestashop 1.7.4.3)

Passgen.php

<?php
    /**
    * Random password generator
    *
    * @param int $length Desired length (optional)
    * @param string $flag Output type (NUMERIC, ALPHANUMERIC, NO_NUMERIC, RANDOM)
    * @return bool|string Password
    */
    function passwdGen($length = 8, $flag = 'ALPHANUMERIC')
    {
        $length = (int)$length;

        if ($length <= 0) {
            return false;
        }

        switch ($flag) {
            case 'NUMERIC':
                $str = '0123456789';
                break;
            case 'NO_NUMERIC':
                $str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
                break;
            case 'RANDOM':
                $num_bytes = ceil($length * 0.75);
                $bytes = getBytes($num_bytes);
                return substr(rtrim(base64_encode($bytes), '='), 0, $length);
            case 'ALPHANUMERIC':
            default:
                $str = 'abcdefghijkmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
                break;
        }

        $bytes = getBytes($length);
        $position = 0;
        $result = '';

        for ($i = 0; $i < $length; $i++) {
            $position = ($position + ord($bytes[$i])) % strlen($str);
            $result .= $str[$position];
        }

        return $result;
    }

    /**
     * Random bytes generator
     * Limited to OpenSSL since 1.7.0.0
     *
     * @param int $length Desired length of random bytes
     * @return bool|string Random bytes
     */
    function getBytes($length)
    {
        $length = (int) $length;

        if ($length <= 0) {
            return false;
        }

        $bytes = openssl_random_pseudo_bytes($length, $cryptoStrong);

        if ($cryptoStrong === true) {
            return $bytes;
        }

        return false;
    }