How to automatically categorized the insert data to their category

I make a simple system for movies. The attributes are id, movie_name, movie_director, movie_starring and movie_genre. I already have data for some movies. But, if the user want to add new movie to the system, they have to fill movie name, director & starring. From the existing data, the system can categorized the movie genre by looking at movie director & starring. For example: Example of existing data

So my question is, how the system can categorized the movie to the correct genre?