How to create random unique alphanumeric string in PHP [duplicate]

Question

I have the following code that lets a user register his/her email on a website with a password, and returns them a unique pin.

<?
if($_POST['srSubmit'] && $_POST['srEmail'] && $_POST['srPass']) {
    $conn = mysql_connect('localhost','','');
    mysql_select_db("db_test",$conn);
    while(1) {
        $pin = rand(111111,999999);
        $sel = mysql_query("SELECT * FROM formusers WHERE pin = '$pin'");
        if(mysql_num_rows($sel) != 0) { continue; }

        mysql_query("INSERT INTO formusers(email,password,pin) VALUES('".$_POST['srEmail']."','".$_POST['srPass']."','".$pin."')");
        if(mysql_affected_rows()!=-1)  {
            echo "Pin:" . $pin;
            exit;
        } else {
            echo "Existing email, try again<br />";
        }
        break;
    }

}
?>
<form method="POST" action="">
<input type="email" name="srEmail" value="" placeholder="Email" /><br />
<input type="password" name="srPass" value="" placeholder="Password" /><br />
<input type="submit" name="srSubmit" value="Register" />
</form>

I want to associate a unique URL with each user (server.com/[unique-9-digit-alphanumeric-code], such that I can create a relatively secure admin page that users can access without necessarily needing to know their password.

Is there an easy way to do this with a PHP function (it doesn't have to be 9 digits, just long and random), or do I need to generate my own random alpha-numeric string and then post that to the database? How would you suggest coding this?

Answer 1

A lot of times, when I need a unique string I use this mysql query: select HIGH_PRIORITY UNIX_TIMESTAMP(); to get a unique 10 digit number like 1374517262 and then append or prepend characters.

Answer 2

http://snipplr.com/view/5444/

This is a nice function that will generate random pronounceable passwords. This may help you get close to what you are trying to accomplish.