My car accelerated by itself when driving when using brakes

Two common things might be the cause of your problem.A throttle plate getting stuck or your idle air control valve as well.Have somebody look at the throttle body and idle valve. Make sure is clean,and if not have it cleaned.Also look at the connector at your idle valve.Some other more complicated but much less possible circumstances exist but always start with the basic and simple things.A throttle body service is a regular maintenance item.Find out when was the last time it was done. Hope this helps you!