Random Password (String) Generator for PHP

Last updated: Dec 2, 2008

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.

    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:


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


Do you use something similar?

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