Thousands of Random Unique Numbers

I'm searching for an efficient way to create thousands of unique random numbers. I would like them to be either all numeric, or a mix of numbers and letters. I would also like to keep the character length around 6 to 10 characters.

Does anybody have a good idea?

 

rand() function would help you

 

I may have figured out the answer to my own question.

http://www.codewalkers.com/c/a/Miscellaneous-Code/Multiple-Unique-Random-Numbers/

 

<?php
function CreateRandomString($instances,$min_length,$max_length)
    {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQUSTUVWXYZ";
        # srand((double)microtime()*1000000); # seed not needed since => php 4.2.0
        $strings = Array();
        for ($inst=0;$inst<=($instances-1);$inst++)
            {
                $i = 0;
                $pass = '' ;
                $randlength = rand($min_length,$max_length);
                while ($i <= $randlength)
                    {
                        $num = rand() % 33;
                        $tmp = substr($chars, $num, 1);
                        $pass = $pass . $tmp;
                        $i++;
                    }
                $strings[$inst] = $pass;
            }
        return $strings;
    }
#
# test it out
#
print_r(CreateRandomString(1000,6,10));
#
# How to use it:
#   $instances:  nubmer of random strings you want to create.
#   $min_length: minimum string length.
#   $max_length: maximum string length.
#   $chars: the charactor database to pick from at random
?>

PHP:

 

If you are storing them in variables, be sure that you don't run out of memory.