How to generate a random serial number

[eluser]skunkbad[/eluser]
I use function to apply a unique user id, and it checks the db to make sure it is truly unique. You may be able to adapt this to your needs:

Code:

public function get_unused_id()
{
    // Create a random user id
    $random_unique_int = mt_rand(1200,999999999);

    // Make sure the random user_id isn't already in use
    $this->CI = get_instance();
    $this->CI->db->where('user_id', $random_unique_int);
    $query = $this->CI->db->get_where($this->CI->config->item('user_table'));
    if ($query->num_rows() > 0)
    {
        $query->free_result();

        // If the random user_id is already in use, get a new number
        $this->get_unused_id();
    }

    return $random_unique_int;
}