Andrew Lloyd Webber often repeats his own melodies, as well as adapting classical melodies. "The Music of the Night" and "All I Ask of You" have similar note progressions. I'm not sure why he did this, since MOTN is the Phantom's love song, while MOTN is Raoul's.
I read about a crazy copyright case (which, if I'm not mistaken, got thrown out of court) in which the studio that owned the copyright sued the composer for violating the copyright in composing later songs that sound similar. What did they expect -- everyone has a signature sound.
Audrey, the Phantom Phanatic, who nonetheless would rather be Jean Valjean, who knew how to make lemonade out of lemons.