just got my mazda 3 2 and a half weeks ago, just last night, i happen to hear a clicking sound whenever i step on the brake pedal when my car is in the P state(Gear in the P position).It wasn't like that when i first got the car.Any advice?

Very normal...this is your shifter locking mech. no worries:D

normal, like mazda service said. shift interlock actuator.