Loop to check dupilicate random strings - php

Question

I have this function which creates random string:
function genID($length) {
$chars = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM#!";
//only allowed chars in the blowfish salt.
$size = strlen($chars); $str = "";
for ($i = 0; $i < $length; $i++)
$str .= $chars[rand(0, $size - 1)]; // strings can be used as char arrays
// Yes, I am aware this salt isn't generated using the OS source.
// use mycrypt_create_iv or /dev/urandom/
return $str;
}
This output something like:
#iBUQvldLq
Now I have users list with something like that:
userid | username | usermail ...
--------------------------------------
#iBUQvldLq test test#gmaik.com ....
Now when some one register I create new string and insert the new string to userid row in database, after that I create a new string, then I check if the new string created doesn't exist, something like this:
function newID()
{
$newid = genID(10);
$query = "SELECT * FROM users WHERE userid = '".$newid."'";
$result1 = mysql_query($query);
$num = mysql_num_rows($result1);
if($num == 1)
{
$newid = genID(10);
return $newid;
}
else
{
return $newid;
}
}
Any one have any idea how to loop on the check function?
I mean the generate function create new random string, then the function check if it already exist, then create new one, if not return the one created.
So now if he create new one, and the new one also match the same other userid, so how I loop until the new string won't match never to other userid string?
Something like loop:
create new string
verify if exist
if exist create new one
if the new one also exist create new one and so on
Till its never match other userid, make a loop, any idea ?
EDITED :
The new function for loop if any need:
function newID(){
$continue = true;
while ($continue) {
$newid = genID(10);
$query = mysql_query("SELECT * FROM users WHERE userid='".$newid."' LIMIT 1");
if (mysql_num_rows($query) != 1)
$continue = false;
return $newid;
}
}
$newid = newID();

Answer 1

It looks like your wanting code like this..
function uHash(){
$continue = true;
while ($continue) {
$hash = substr(MD5(microtime()), 0, 7);
$query = mysql_query("SELECT `Link` FROM Table WHERE `value`='$hash' LIMIT 1");
if (mysql_num_rows($query) != 1)
$continue = false;
return $hash;
}
}
The script will loop until it finds a unique value.

Answer 2

Setting your user_id column as an auto_increment field would solve this issue. [Best Approach]
If you really want to do with PHP, couple uniqid() with rand() to generate a unique seed that doesn't collide.
Something like this
<?php
echo $id = uniqid(rand(), true);
?>

Answer 3

Just you can use for unique id
<?php
function genID() {
return uniqid();
}
echo genID();
?>