Something

function get_dir_size($dir_name){
        $dir_size =0;
           if (is_dir($dir_name)) {
               if ($dh = opendir($dir_name)) {
                  while (($file = readdir($dh)) !== false) {
                        if($file != "." && $file != ".."){
                              if(is_file($dir_name."/".$file)){
                                   $dir_size += filesize($dir_name."/".$file);
                             }
                             /* check for any new directory inside this directory */
                             if(is_dir($dir_name."/".$file)){
                                $dir_size +=  get_dir_size($dir_name."/".$file);
                              }
                           }
                     }
             }
       }
closedir($dh);
return $dir_size;
}