Here is a function I wrote to generate a random string in PHP. It is probably most useful for generating passwords. You can specify the length of the resulting string, as well as what characters are allowed. The default length is eight and the default character set is alphanumeric.

<?php

function random_string($length = 8, $chars = null) {
    if( empty($chars) ) $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    while( strlen($s) < $length) {
        $s .= substr($chars, rand(0, strlen($chars) - 1), 1);
    }
    return $s;
}

// Example
echo random_string(10);

?>