unique ID whit numbers and letters?

marxx · 03-09-2008, 02:45 PM

Hi all!

Today my problem is to generate unique ID which contains numbers and letters (ie. 101MH).

As far as I know (well, i don't know much tho), mysql wont let use auto-increment with letters? So, here is couble thoughts what came up but don't quite know how to make these.

First, script checks all IDs from database and picked up biggest ID.

Code:

100MH
101MH
102MH
103MH <- this one

after that, we would use that, explode it and increase that number to 104, add MH again to it and use it as new unique ID.

Second thing what came in my mind was use do while??

So if someone has some suggestions, please could you share it for me? =)

And I know, would be simple to NOT use those letters but I have my reasons! ;)

Thanks for all help (again!)

freenity · 03-09-2008, 02:58 PM

the letters don't change??
I guess the best way would be storing only numbers in the db, and then when you select or refer to the id add MH at the end.

maZtah · 03-09-2008, 05:18 PM

I agree with freenity if the letters don't change.

Else i would do something like:

PHP Code:


			
// first select the last id

$szQuery = 'SELECT id FROM table ORDER BY id DESC LIMIT 1';

$pResult = mysql_query($szQuery);



// fetch the result

$aRow = mysql_fetch_array($pResult);



// get the integer and the letters (there are much better ways to do this, but can't come up with one right now;()

$iId = substr($aRow['id'],0,strlen($aRow['id'])-2);

$szLetters = substr($aRow['id'],-2)



// add 1 to the integer

$iId += 1;



// add the letters again

$szId = $iId . $szLetters;



// and finally, insert the new id

$szQuery = 'INSERT INTO table (id) VALUES ("'.$szId.'");

mysql_query($szQuery);

Well, just typed in this textarea, haven't tested it, but you should figure any bugs out!

Good luck!

sjaq · 03-09-2008, 06:14 PM

I made a class a while ago, which generates strings from id's and id's from strings. The coding is pretty crappy, but I was just beginning with php then, so please spare me :).

Here it is:

PHP Code:


			
<?php 

    class GenID {
        
        // array of usable characters, mix them together to get more random results
        // you can add uppercase chars to increase the number of possibilities
        private $useChars = array(
            26 => 'a',
            11 => 'b',
            8 => 'c',
            20 => 'd',
            10 => 'e',
            18 => 'f',
            25 => 'g',
            3 => 'h',
            30 => 'i',
            5 => 'j',
            32 => 'k',
            1 => 'l',
            23 => 'm',
            14 => 'n',
            28 => 'o',
            16 => 'p',
            33 => 'q',
            4 => 'r',
            19 => 's',
            6 => 't',
            21 => 'u',
            29 => 'v',
            34 => 'w',
            24 => 'x',
            0 => 'y',
            12 => 'z',
            27 => 1,
            15 => 2,
            22 => 3,
            9 => 4,
            31 => 5,
            2 => 6,
            17 => 7,
            13 => 8,
            35 => 9,
            7 => 0
        );
        
        // reserved id's with the id that generates it as key
        private $reserved = array(
            'home' => 177094,
            'index' => 51067968, 
            'user' => 1004764,
            'users' => 36171523,
            'admin' => 44634038,
            'porn' => 782942,
            'about' => 44220282,
            'id' => 1100,
            'get' => 32766,
            'in' => 1094,
            'out' => 37050,
            'search' => 1166872035
        );
        
        private $linkCCount;
        private static $instance;
        
        private function __clone() {}
        
        public static function get($id) {
            if(self::$instance === null) {
                self::$instance = new GenID;
            }
            return self::$instance->run($id);
        }
        
        private function run($id) {
            if(is_string($id)) {
                return $this->strtoid($id);
            } else {
                $id = intval($id);
                return $this->idtostr($id);
            }
        }
        
        private function fixId($id) {
            if(in_array($id, $this->reserved)) {
                $nid = $id+1;
                return $this->fixId($nid);
            } else {
                return (int)$id;
            }
        }
        
        private function clean($url) {
            return preg_replace('/([\W\s])/', '', $url);
        }
        
        private function idtostr($id, $nofix = false) {
            if($nofix == false) {
                $id = $this->fixId($id);
            }
            if(!isset($this->linkCCount)) {
                $this->linkCCount = count($this->useChars);
            }
            $this->link = '';
            $this->idtostrsub($id);
            return strrev($this->link);
        }
        
        private function strtoid($str) {
            if(!isset($this->linkCCount)) {
                $this->linkCCount = count($this->useChars);
            }
            $str = strtolower($str);
            $str = $this->clean($str);
            if(strlen($str) === 0) {
                return false;
            } elseif(strlen($str) === 1) {
                return array_search($str, $this->useChars);
            }
            $chars = array();
            foreach(str_split($str) as $k => $v) {
                if(in_array($v, $this->useChars)) {
                    $chars[] = array_search($v, $this->useChars);
                }
            }
            $s = $chars[0];
            unset($chars[0]);
            // start the math

            foreach($chars as $char) {
                $s = ($s * $this->linkCCount) + $char;
            }

            return $s;
        }

        private function idtostrsub($id) {
            $id = (int)$id;
            // if the id is smaller then the amount of chars just give it a char
            if($id < $this->linkCCount && $id >= 0) {
                if($id == $this->linkCCount) $id = 0;
                $this->link .= $this->useChars[$id];
            } else {
                // devide the id by the amount of chars
                $flr = floor($id / $this->linkCCount);
                $res = $id - ($flr * $this->linkCCount);
                if($res == $this->linkCCount) { $res = 0; }
                $this->link .= $this->useChars[$res];
                $this->link .= ($flr < $this->linkCCount && $flr >= 0)? 
                /* true */    $this->useChars[$flr] :
                /* false */    $this->idtostrsub($flr);
            }
        }
        
    }
    
    /* Example Usage */
    
    $id = GenID::get('henkifsf'); // result: 257762013534
    $str = GenID::get(54646446); // result: ks4pi

?>

It saves a lot of characters, as you can see in the example the id: 257762013534 has the string 'henkifsf'.