I want to develop a bot which will update the status of a facebook account using php.
Please guide me on this
@Porkchop is correct, you will probably need the Facebook Connect API. To update a users status on Facebook, you should look at the Status.set API call.
For coding a googletalk bot in php there are some articles that should get you started:
But also consider using IMified, which does a lot of the work of creating and running chat bots for you.
If all you are interested in is a simple way to update your Facebook status from you Google Talk status, you probably don't need to go to all that work - just install the 'Google Talk Status Synchronizer' facebook application.