Generate random 5 characters string

Question

I want to create exact 5 random characters string with least possibility of getting duplicated. What would be the best way to do it? Thanks.

Answer 1

$rand = substr(md5(microtime()),rand(0,26),5); 

Would be my best guess--Unless you're looking for special characters, too:

$seed = str_split('abcdefghijklmnopqrstuvwxyz'                  .'ABCDEFGHIJKLMNOPQRSTUVWXYZ'                  .'0123456789!@#$%^&*()'); // and any other characters shuffle($seed); // probably optional since array_is randomized; this may be redundant $rand = ''; foreach (array_rand($seed, 5) as $k) $rand .= $seed[$k]; 

Example

And, for one based on the clock (fewer collisions since it's incremental):

function incrementalHash($len = 5){   $charset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";   $base = strlen($charset);   $result = '';    $now = explode(' ', microtime())[1];   while ($now >= $base){     $i = $now % $base;     $result = $charset[$i] . $result;     $now /= $base;   }   return substr($result, -5); } 

Note: incremental means easier to guess; If you're using this as a salt or a verification token, don't. A salt (now) of "WCWyb" means 5 seconds from now it's "WCWyg")