Function To Generate Random String

**ksg91** · 27-12-10, 10:17

I was working on Url Shortner script and I needed a better algorithm that can generate a fixed length random string which have very less probability of collision with other strings in db. So I created one simple, yet efficient algorithm. I hope this is good. It returns you 8 character long random string.

PHP Code:

 <?php

//////////////////////////////////////

// Author: Kishan Gor a.k.a Ksg91

// Date: 27-12-2010

/////////////////////////////////////

 
//returns 8 character long random string

function getKSGRandomString()

{

  $a=array("0"=>"0","1"=>"1","2"=>"2","3"=>"3","4"=>"4","5"=>"5","6"=>"6","7"=>"7","8"=>"8","9"=>"9","10"=>"a","11"=>"b","12"=>"c","13"=>"d","14"=>"e","15"=>"f","16"=>"g","17"=>"h","18"=>"i","19"=>"j","20"=>"k","21"=>"l","22"=>"m","23"=>"n","24"=>"o","25"=>"p","26"=>"q","27"=>"r","28"=>"s","29"=>"t","30"=>"u","31"=>"v","32"=>"w","33"=>"x","34"=>"y","35"=>"z","36"=>"A","37"=>"B","38"=>"C","39"=>"D","40"=>"E","41"=>"F","42"=>"G","43"=>"H","44"=>"I","45"=>"J","46"=>"K","47"=>"L","48"=>"M","49"=>"N","50"=>"O","51"=>"P","52"=>"Q","53"=>"R","54"=>"S","55"=>"T","56"=>"U","57"=>"V","58"=>"W","59"=>"X","60"=>"Y","61"=>"Z");

  $rand1=mt_rand(00000000,99999999);

  $rand2=mt_rand(00000000,99999999);

  $string='';

  while($rand1>0)

  {

    $x = $rand1 % 100;

    $rand1=floor($rand1/100);

    $x = $x % 60; 

    $string.=$a[$x];

  }

  while($rand2>0)

  {

    $x = $rand2 % 100;

    $rand2=floor($rand2/100);

    $x = $x % 60; 

    $string.=$a[$x];

  }

  return $string;

}

?>

Expecting your advices and suggestions to improve it more.

**frostymarvelous** · 27-12-10, 11:21

Won't this take too much time?
I would have done something like this.

$x= 0;
$string= '';
While($x <= $len )
{
$v= rand(0,64);
$string .= $a[$v];
$x ++;
}

Nothing fancy.
I'm mobile so pardon any errors, I'm just typing straight. And yes I know a for loop would be better. Hehe.

**razzbee** · 27-12-10, 13:05

Well i guess frost is correct but i will prefer this
<?php
$rand1=rand(0,999);
$rand2=rand(0,999);
$rand3=rand(1,10);
$rand_string=pow($rand1,$rand2);
$rand_string=substr($rand_string,1,$rand3);
sorry on mobile pardon me 4 the errors.

**subzero** · 27-12-10, 13:29

lol

foreach('$a as $a');

**frostymarvelous** · 27-12-10, 14:18

I just noticed you tagged it url shortener, so performance won't be an issue to you.
Rather, the uniqueness is important. Cool.

**Anshul** · 27-12-10, 16:50

you may try using mcrypt based encryption

**metulj** · 27-12-10, 17:33

does it have to be random string?
is there any advantage of randomizing?

i mean, currently im also working
on URL shortener script...
but basicly i dont mind if it starts like

domaine.com/1
domaine.com/2
etc, etc
...........
domaine.com/1359
etc...

im also trying to add option to create manual URL..
for example if i have some tralala.zip to link...
it'll be domaine.com/tralala.zip <<== ofcourse if that name still available I.E. not yet in DB

**frostymarvelous** · 27-12-10, 21:16

I don't think there's anything wrong with randomising but you should always check the Db to ensure it is unique.

Do something like yourls. Start with single char and then progress.

**ksg91** · 28-12-10, 07:45

Originally Posted by frostymarvelous [Only registered and activated users can see links. Click Here To Register...]

Won't this take too much time?
I would have done something like this.

$x= 0;
$string= '';
While($x <= $len )
{
$v= rand(0,64);
$string .= $a[$v];
$x ++;
}

Nothing fancy.
I'm mobile so pardon any errors, I'm just typing straight. And yes I know a for loop would be better. Hehe.

actually, my algorithm was to convert an integer string into random character string. I was actually going to pass integer and get its string but then created like that. You have bit faster implementation of above function but algorithm is that get 16 digit integet, make pair of two integer and take modulo 60 (because we have 61 character in above array) and append it to string.

Originally Posted by razzbee [Only registered and activated users can see links. Click Here To Register...]

Well i guess frost is correct but i will prefer this
<?php
$rand1=rand(0,999);
$rand2=rand(0,999);
$rand3=rand(1,10);
$rand_string=pow($rand1,$rand2);
$rand_string=substr($rand_string,1,$rand3);
sorry on mobile pardon me 4 the errors.

can you explain this code?

Originally Posted by subzero [Only registered and activated users can see links. Click Here To Register...]

lol

foreach('$a as $a');

Didnt got what you wanted to post.

Originally Posted by Anshul [Only registered and activated users can see links. Click Here To Register...]

you may try using mcrypt based encryption

thanks. will check about that.

Originally Posted by metulj [Only registered and activated users can see links. Click Here To Register...]

does it have to be random string?
is there any advantage of randomizing?

i mean, currently im also working
on URL shortener script...
but basicly i dont mind if it starts like

domaine.com/1
domaine.com/2
etc, etc
...........
domaine.com/1359
etc...

im also trying to add option to create manual URL..
for example if i have some tralala.zip to link...
it'll be domaine.com/tralala.zip <<== ofcourse if that name still available I.E. not yet in DB

Randomizing string has advantage of less guess/hit ratio. If its in sequence, one can guess any valid link. And some people wont like sharing their shorted link with everyone.
And I am making it very basic, just wanted to make it for personal use but not limited to me only.

**frostymarvelous** · 28-12-10, 08:12

I can't quote the whole post and I'm mobile but in reply to the reply you made to me.
Wow. That must have involved some thinking right there. Mine was just off the bat.
I. Saving this for future reference. Never knlw when it will come in handy. Either for use or for study.

Btw. I studied oop just by looking at ksg's code. He's that good.