Question: In my application, there are 5 tabbar items. When I am in 2nd tabbar item and I perform some operation in that tab, I have to get controller of 1st tab, so that I will be in the 1st tab. How might I achieve this?

Answer: 
Use the FOSUserBundle.... It handles all user related features. Custom queries are done in it's own repository like UserRepository. Then its linked to the Entity and can be called from the controller with $em->getRepostory('path to entity')->myQuery(). Its all in the Symfony docs. 

FOSUserBundle: <https://github.com/FriendsOfSymfony/FOSUserBundle>
Start with Symfony2's Doctrine documentation:

<http://symfony.com/doc/current/book/doctrine.html>