random key generator

[zzz]

Yes, the keys are stored. So far I've had about 6K of them but this is a good wake-up call for me. What I'll do is run the script, generate ID, query db for such value and if not found -- use it, if it is found, call the function again and repeat the steps.

Thanks for confirming my thought trend.

[NogDog]

Of course, there's a possibility, especially as more values get used, that you could get a sequence of several duplicates while trying to generate one of these, resulting in several database queries.

[Kudose]

I have yet to come across a duplicate when using the MySQL equivalent to UUID()

/**
   *  uuid
   *
   *  uuid() simply replicates MySQL's UUID function, which returns a 36
   *  character "random" hash (32 alphanumeric, 4 dashes).
   *  @return string
   */
  function uuid(){
    return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
      mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff),
      mt_rand(0, 0x0fff) | 0x4000,
      mt_rand(0, 0x3fff) | 0x8000,
      mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff));
  }

Laserlight and I have discussed this before and there is always a chance of getting a duplicate ... but using UUID(), there are more combinations than known stars in the universe.

[zzz]

I need a human readable key, with specified str length. What would the key look like in your code example?

[zzz]

OK, I'm working myself into a loop...

Here are the steps I need to accomplish:

1. Generate key
2. Check if the key exists
   if YES -- repeat step 1 and 2
   if NO -- use the key

Here's how I generate the key:

function generator($lenght=5)
{
     for($i = 0; $i < $lenght; $i++)
     {
          $uniqueKey .= chr(rand(97,122));
     }
     return $uniqueKey;
}

$randomKey = generator(); 

Here's how I check if the key is stored in db:

if ($randomKey == $db->get_var(“SELECT key FROM t1 WHERE key = '".$randomKey."' ") )
{
	// found match	-- re-generate key		
} else {
	// did not find match -- use key	
}

Need help putting it together without writing endless loops...

[dagon]

testkey($key){
if ($randomKey == $db->get_var(“SELECT key FROM t1 WHERE key = '".$randomKey."' ") )
{
  $randomKey = generator(); 
testkey($randomKey);
} else {

// did not find match -- use key    
}
}

[zzz]

Dah... coffee. i need more coffee.

[Kudose]

zzz;10936308 wrote:

I need a human readable key, with specified str length. What would the key look like in your code example?

4386bff0-e5fb-11de-8a39-0800200c9a66 see http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid

[dagon]

the problem is he wanted one 5 chars long.

i use md5() on either mysql's UUID() or php's uniqid

but if you want a human to use it, it's not very friendly.

[johanafm]

And the problem is not circumventable with 5 characters. I do not know how many keys he has, or expect to have. But with a 5 character key, collisions will start to become somewhat frequent at about 3500 existing keys; see Laserlight's post above.
Moving up to an 8 character key, this threshold is moved up to about 450000 keys. A decent improvement.

[Kudose]

dagon;10936324 wrote:

the problem is he wanted one 5 chars long.

i use md5() on either mysql's UUID() or php's uniqid

but if you want a human to use it, it's not very friendly.

Granted the OP's default value for his function is 5 characters, I didn't see anywhere where the OP stated it had to be 5 characters, so I suggested UUID.

If you are going to have a substantial amount of users, you are not going to want a 5 or 8 character key for them. Just imagine you are the one in a million chance that your site gets as popular as Facebook is or MySpace was. I highly doubt the numbers 5 or 8 entered their mind for a user key.

But ... to each his own.

[dagon]

Kudose;10936408 wrote:

Granted the OP's default value for his function is 5 characters, I didn't see anywhere where the OP stated it had to be 5 characters, so I suggested UUID.

If you are going to have a substantial amount of users, you are not going to want a 5 or 8 character key for them. Just imagine you are the one in a million chance that your site gets as popular as Facebook is or MySpace was. I highly doubt the numbers 5 or 8 entered their mind for a user key.

But ... to each his own.

agreed, but he said 'human readable' so the assumption i was working with was 5 would be the default, or at least to few characters to use uuid. Humans are so annoying!

[zzz]

The key is a part of a unique URL. It has to be short because users often write that URL down. And yes, humans can be difficult sometimes.

[zzz]

I have a new case where I could use long unique IDs for naming images. I gave it a whirl and although the images are processed correctly and values stored in DB OK, I can't seem to be able to access images online with such name. Are there naming conventions that prevent such naming for images?

Kudose;10934541 wrote:

I have yet to come across a duplicate when using the MySQL equivalent to UUID()

/**
   *  uuid
   *
   *  uuid() simply replicates MySQL's UUID function, which returns a 36
   *  character "random" hash (32 alphanumeric, 4 dashes).
   *  @return string
   */
  function uuid(){
    return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
      mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff),
      mt_rand(0, 0x0fff) | 0x4000,
      mt_rand(0, 0x3fff) | 0x8000,
      mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff));
  }

Laserlight and I have discussed this before and there is always a chance of getting a duplicate ... but using UUID(), there are more combinations than known stars in the universe.

[Kudose]

I cannot think of a reason an image named XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX.jpg would not load.

What happens when you try to access the image address directly?

[bradgrafelman]

If the entire URI is less than 255 or so characters, then no, the length won't be a problem.