prevent the id is not used (#8)

index.php

@@ -37,7 +37,11 @@
         // Upload File
         if ($_SERVER['REQUEST_METHOD'] === 'PUT') 
         {
-                $rnd_data = mt_rand(10000,99999);
+                do
+                {
+                        $rnd_data = mt_rand(00000,99999);
+                } while (file_exists(_DATA_DIR . "/" . $rnd_data));
+                
                 $filesize = 0 ;
                 
                 mkdir(_DATA_DIR . "/" . $rnd_data);