How to generate unique random numbers using php

Mohammed Adamu

9y5.5kPHP

Please i need help on how to generate highly unique id for my php program, i have one which is doing that but after about 190 unique numbers it started to repeat itself which is making the unique column in the database problematic. please here is my code code if there is something i did wrong please help me correct it thanks. "

function uniqids() {

$chars = "003232303232023232023456789";

srand((double)microtime()*1000000);

$i = 0;

$pass = '' ;

while ($i <= 7) {

$num = rand() % 33;

$tmp = substr($chars, $num, 1);

$pass = $pass . $tmp;

$i++;

}

return $pass;

}

$finalcode='RS-'.uniqids();

8 Replies

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Kesavan Krishnan9y ago
Accepted answer
The best way to generate PHP unique number as follows
echo md5(uniqid(mt_rand(), true).microtime(true));
?>
Mohammed Adamu9y ago
@Kesavan Krishnan on this assurance I say thanks a lot for your help.
Kesavan Krishnan9y ago
@Mohammed Adamu - Definetly it will not repeat because we are taking "microtime(true)". This return number changed in every seconds and also we used "uniqid('', true)". So we will have safe and unqiue value in every seconds.

Check the following code.
    $unique = [];
   for($i = 0; $i<100; $i++){
      $unique[$i] = md5(uniqid(mt_rand(), true).microtime(true));
      echo $unique[$i].PHP_EOL;
   }

   print_r(array_diff($unique, array_unique($unique)));

?>
Mohammed Adamu9y ago
Wow Mr. Kesavan Krishnan that is great and it also long enough but if i may ask can't it repeat it self with time or you are 100% sure it will not happen. because i realy want to implement it in my application. Thanks
Mohammed Adamu9y ago
ok thanks man i have used another method which is ok, the autoincreament generated mysql is what am using as my unique id
Bryian Tan9y ago
Is random right, no guarantee, you either make the range larger or change the strategy like using uniqid() function

https://www.w3schools.com/php/func_misc_uniqid.asp

Or, check if the id exists before insert into table.
Mohammed Adamu9y ago
Ok please if i may asked what difference will do to include this $num = rand(1000000, 99999999) %33; i have added it but i think it still generating but what is the assurance that it will not repeat itself. Thanks a lot.
Bryian Tan9y ago
Have you try to include min and max?

$num = rand(1000000, 99999999) %33;

http://php.net/manual/en/function.rand.php