Random Password (String) Generator for PHP

Random string generators are something we programmers end up using quite a bit. Sometimes you want to generate a random file name, a random email verification link, a random password, random token, etc.. Here is the one that I have been using lately.

This password generator uses the Mersenne Twister algorithm to generate random digits. You can learn more about it at Wikipedia or on Makoto Matsumoto’s website.

<?php
function randomString($length = 10, $chars = '1234567890') {

    // Alpha lowercase
    if ($chars == 'alphalower') {
        $chars = 'abcdefghijklmnopqrstuvwxyz';
    }

    // Numeric
    if ($chars == 'numeric') {
        $chars = '1234567890';
    }

    // Alpha Numeric
    if ($chars == 'alphanumeric') {
        $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
    }

    // Hex
    if ($chars == 'hex') {
        $chars = 'ABCDEF1234567890';
    }

    $charLength = strlen($chars)-1;

    for($i = 0 ; $i < $length ; $i++)
        {
            $randomString .= $chars[mt_rand(0,$charLength)];
        }

    return $randomString;
}

echo randomString(8,'numeric');
?>

Syntax is randomString([int],[predifined | custom char set]);

For example to create an 8 character alpha numeric string you could use:

randomString(8,'alphanumeric');

Of if you wanted a string with only a small subset of characters you could use:

randomString(8,'abco0iLlI');

Do you use something similar?