Why is the original version of Love Never Dies different than songs in movie?

The original version of Love Never Dies is not a movie. It is a musical that premiered in 2010 at the Adelphi Theatre in London, England. It was written by Andrew Lloyd Webber and Glenn Slater and is a sequel to the original The Phantom of the Opera musical written by Lloyd Webber and Charles Hart in 1986. The musical tells the story of The Phantom ten years after the original musical and features many new songs not found in the original opera.