Anonymous users close message for all other anonymous users

I use cookie to save anonymous closes.
just add these code at the begining of admin_message.module file.

 define('ADMIN_MESSAGE_COOKIE',       'admin_message_notification');
function _admin_message_set_cookie($message_nid) {
    $cookie = array();
    if (isset($_COOKIE[ADMIN_MESSAGE_COOKIE])) {
        $cookie = unserialize($_COOKIE[ADMIN_MESSAGE_COOKIE]);
    }
    $cookie += array(
    $message_nid => time(),
  );

  $cookie_lifetime = 86400000;
  setcookie(ADMIN_MESSAGE_COOKIE, serialize($cookie), time() + $cookie_lifetime, '/');
}
function _admin_message_read_cookie($nid) {
  global $user;
  if($user->uid){
      return TRUE;
  }
  if (!isset($_COOKIE[ADMIN_MESSAGE_COOKIE])) {
    return TRUE;
  }

  $cookie = unserialize($_COOKIE[ADMIN_MESSAGE_COOKIE]);

  if (empty($cookie)) {
    // Nothing to do ...
    return TRUE;
  }
  if(array_key_exists($nid, $cookie))
  {
     return FALSE;
  }

    return TRUE;
}

then patch current "admin_message_close" function by following code

function admin_message_close($nid) {
  global $user;
  if($user->uid){
      db_query('DELETE FROM {admin_message_close} WHERE nid = %d AND uid = %d', $nid, $user->uid);
      db_query('INSERT INTO {admin_message_close} (nid, uid) VALUES (%d, %d)', $nid, $user->uid);
  } else{
      _admin_message_set_cookie($nid);
  }
  drupal_goto();
}

and finaly change line 112 to this
if (empty($closed_by_user) && ($item->created >= $user->created || $item->keep_new) && $php_visibility && _admin_message_read_cookie($item->nid)) {

I've made a patch out of the approach described in comment #3. It's a little bit different than what b.ravanbakhsh did:

• It uses PHP's built in support for Array Cookies rather than serialize() and unserialize(). According to the PHP docs on setcookie() this is preferred because of potential security problems with serialize/unserialize.
• It uses a static cache for the cookie variable and centralizes accessing the cookie to the _admin_message_set_cookie() function and a minimal _admin_message_get_cookie() which is really just a wrapper around the first function.

Please let me know what you think!

Best regards,
David.

Patch from #4 committed! Thanks, b.ravanbakhsh!