/**
  * Remove a relationship between two users and clear caches afterwards.
  *
  * @param $user1 Integer: user ID of the first user
  * @param $user2 Integer: user ID of the second user
  */
 public function removeRelationshipByUserID($user1, $user2)
 {
     global $wgUser, $wgMemc;
     if ($user1 != $wgUser->getID() && $user2 != $wgUser->getID()) {
         return false;
         // only logged in user should be able to delete
     }
     // must delete record for each user involved in relationship
     $dbw = wfGetDB(DB_MASTER);
     $dbw->delete('user_relationship', array('r_user_id' => $user1, 'r_user_id_relation' => $user2), __METHOD__);
     $dbw->delete('user_relationship', array('r_user_id' => $user2, 'r_user_id_relation' => $user1), __METHOD__);
     $wgMemc->delete(wfForeignMemcKey('huiji', '', 'relationship', 'profile', "{$user1}-1"));
     $wgMemc->delete(wfForeignMemcKey('huiji', '', 'relationship', 'profile', "{$user2}-1"));
     $wgMemc->delete(wfForeignMemcKey('huiji', '', 'relationship', 'profile', "{$user1}-2"));
     $wgMemc->delete(wfForeignMemcKey('huiji', '', 'relationship', 'profile', "{$user2}-2"));
     // RelationshipRemovedByUserID hook
     wfRunHooks('RelationshipRemovedByUserID', array($user1, $user2));
     // Update social statistics for both users
     $stats = new UserStatsTrack($user1, '');
     $stats->updateRelationshipCount(1);
     $stats->updateRelationshipCount(2);
     $stats->clearCache();
     $stats = new UserStatsTrack($user2, '');
     $stats->updateRelationshipCount(1);
     $stats->updateRelationshipCount(2);
     $stats->clearCache();
 }