@bilalsaaeed
First of all ... change your plugs, air filter, oil (get some with less viscosity, a 10W30 Caltex Havoline Formula is a good choice) ... get the throttle body cleaned ... unless your battery is old, no need to change it ... oh and ofcourse get the idle increased.
If problem still persists ... then, you need to get the vaccum piping checked, something there could be the fault (I doubt it though, usually such a fault would effect your cars normal performance horribly in general)
@sunny
Sounds like a vaccum piping problem, get it checked. Basically when you press the brakes ... the pressure changes effecting your cars vaccum reading and hence the idle.