random script don't run

php random script running slowly

here seems to be the problem

<?php   
   function sortear($prevItems, $number) {
     for ($k=0; $k<sizeof($prevItems); $k++) {
       if ($prevItems[$k] == $number)
          return true;
     }
       return false;
   }
   for ($i=0; $i<=9; $i++) {       
      $num[$i] = rand($_GET['inicial'],$_GET['final']);      
      while (sortear($prevItems, $num[$i])) {          
         $num[$i] = rand($_GET['inicial'],$_GET['final']);       
      }       
    $prevItems[$i] = $num[$i];
    }

   sort($num);

?> 

any sugestion for this random? rest of code here

link