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Hi I have a function that will generate a random string which works fine. What I would like to do is store that string as the primary key in my database. The problem is that I first need to make sure that the string is unique before storing it. Here is what I have so far. I'm sure I need a loop until result = <0 but not sure how to go about that any help would be much appriciated. I'm also open to a better solution as I think this may be a slow solution. 

//generate random slug
function genRandomString($length=10,$characters = '0123456789abcdefghijklmnopqrstuvwxyz',$string = '') {
    for ($p = 0; $p < $length; $p++) {
        $string .= $characters[mt_rand(0, strlen($characters))];
    }

    return $string; } 

 //store slug into variable
 $slug = genRandomString('5');      

 //select the slug that is equal to our slug
 $qry = "SELECT `slug` FROM `drink_data` WHERE `slug` = '$slug'";       
 $result = mysql_query($qry);
    //if reslut make a new slug (this dosen't recheck the new slug which is a problem)
        if($result >= 0){
             $slug = genRandomString('5');

        }
Brooke.
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  • I'm fairly new to this, I looked up what a GUID is can you provide an example? – Brooke. Aug 18 '11 at 07:20
  • As a side note, if that field in db is a primary or unique, db will error out if you try to enter a duplicate. You can use this regardless of your unique generator. – Halil Özgür Aug 18 '11 at 07:21
  • @battal, Yeah the idea is to prevent the DB error from showing :) – Brooke. Aug 18 '11 at 07:22
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    You'd want to hide db errors any way, I was implying an usage like in the Stefan Mai's answer below :) – Halil Özgür Aug 18 '11 at 07:26
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    At last, I was looking for this link for minutes: http://kevin.vanzonneveld.net/techblog/article/create_short_ids_with_php_like_youtube_or_tinyurl/ (also mentioned in a SO question http://stackoverflow.com/questions/4153628/php-short-id-like-youtube-with-salt) – Halil Özgür Aug 18 '11 at 07:28

1 Answers1

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First, instead of $result >= 0, use mysql_num_rows($result) >= 0). Next, you'll likely want to wrap this whole thing in a while:

do{
  $slug = genRandomString(5);      
  //select the slug that is equal to our slug
  $qry = "SELECT `slug` FROM `drink_data` WHERE `slug` = '$slug'";       
  $result = mysql_query($qry);
}while(mysql_num_rows($result) > 0);

This will keep generating new slugs (and checking their uniqueness) until it finds something. You'll probably want to add code to bail on saturation (5 numbers isn't that long, you'll fill up quickly and this loop will run exponentially slower).

Stefan Mai
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