Entering into a mirror effect

This will require careful planning and executing the shot of the actor moving up to the mirror, the mirror (a clean plate) and the actor appearing to walk through the mirror in an environment where you can easily remove the background. You'll also need to plan on filming the elements that may be reflected in the mirror so you can build the composite. The distance from the camera, the angle and the exposure and lighting are critical to successfully pulling this off. You cannot just shoot one shot of an actor walking up to a mirror and apply some effects. To reproduce your sample I would need to have at least 3 different shots.