CAKEPHP create unique code on entries in database

ok sorry, wrote too little info here and i have done some research:

The question: What is the easiest way to write a model function that creates an unique code (5 characters) for each row in a cake model/table that doesnt already have a code?

    //create a unique code

    //set the random id length 
    function generateCode()
    {


    while($i > 0)
    {
    $random_id_length = 7; 
    //generate a random id encrypt it and store it in $rnd_id 
    $rnd_id = crypt(uniqid(rand(),1)); 
    //to remove any slashes that might have come 
    $rnd_id = strip_tags(stripslashes($rnd_id)); 
    //Removing any . or / and reversing the string 
    $rnd_id = str_replace(".","",$rnd_id); 
    $rnd_id = strrev(str_replace("/","",$rnd_id)); 
    //finally I take the first 7 characters from the $rnd_id 
    $rnd_id = substr($rnd_id,0,$random_id_length); 

//check if the code is unique
    $i = $this->checkCode($rnd_id);
    }


    return $rnd_id;

    }

    //check to see if the code isnt already in the database
    function checkCode($code)
    {
     $conditions = array("uniqueCode" => $code));
     $result = $this->Visitors->count('all', array('conditions' => $conditions)); 

     return $result;
    }

//check how many has a code
function check()
{
  $conditions = array("NOT" => array ("uniqueCode" => null));
     $result = $this->Visito开发者_运维技巧rs->count('all', array('conditions' => $conditions)); 

     return $result;
}

function update()
{

//update until everyone has a code
  while( $i > 0)
{

   $this->generateCode()
    // get next visitors that DONT have a code.
    $conditions = array ("uniqueCode" => null));
    $visitor = $this->Visitors->find('first', array('conditions' => $conditions)); 
    $i = $this->check();

}

echo 'Done';


}

Cant make it work properly and it must be an easier way?

How about an id column? :]

If You want it to be like a hash thing, I think use this:

substr(str_shuffle("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789,;:!?.$/*-+&@_+;./*&?$-!,"), 0, 5);

and you shouldn't worry about checking whether it's unique. Or do it, so create a hash like that and try to find it in the table, if it's not in there - your good to go.

in your Model, you can do something like this

<?php

function beforeSave() {
    if (empty($this->data[$this->alias]['id'])) {
        $this->data[$this->alias]['id'] = base_convert(uniqid(), 16, 36);
    }
    return $this->data;
}
?>

This will generate a unique id of 10 chars. You can figure out how to create a unique id of 5 chars, maybe converting the string to a higher base, but I find it difficult because you'll have to make your own function, base_convert has a limit of 36

One thing to think about is the length of the code. A five character code, assuming you use upper and lower case characters in it, has 380,204,032 possible unique codes. If you create these codes truly randomly, you'll rather soon hit the point where you're creating duplicates. There's a 50% chance of collision after you have generated 22,959 codes.

So, since for each new code you need to check whether it already exists or not,
(BTW, a much more elegant check is this):

do {
    $code = /* create code */;
} while (!$this->isUnique(array('code' => $code)));

over time you'll hit more and more already existing codes, slowing down the generation of each code, to the point where you may have to loop 100 or more times to find a unique code (99% chance of collision at only 59,177 codes).

If you're just talking about a few thousand records max, I wouldn't worry about it. If your dataset could/is supposed to grow beyond that though, you should think either about a different scheme for your codes (UUIDs come to mind), generate codes sequentially or pre-generate a list of all possible codes, shuffle it and use up codes one by one.

There are a gazillion ways to do this and all you have to do is google the appropriate words. I found it in the PHP manual, so that would be a good place to start.

To make it unique, it would be based on date and would incorporate some sort of hashing.

Do some searching, reading and learning.