php - Creating random character unique URLS -

how generate random 12 character char url of page record in database how youtube 11 characters https://www.youtube.com/watch?v=kdjirnjcanw

i want unique each entry in database , consist of letters of upper , lower case, numbers , maybe (if not bad security) special characters.

function:

function generaterandomstring($length = 12) {     $characters = '0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz';     $characterslength = strlen($characters);     $randomstring = '';     ($i = 0; $i < $length; $i++) {         $randomstring .= $characters[rand(0, $characterslength - 1)];     }     return $randomstring; } 

then call it:

$randomstring = generaterandomstring(); 

slightly adapted stephen watkins' solution here