P.S. stands for Post-scriptum, latin word for "written after". In a letter you use it when you forgot to write something and already signed your letter; then you add "P.S. what you forgot". With emails it's obviously not useful, but it's still used to emphasize on something. In your sentence, of course it's hard to forget to say "I love you", so it's just used to emphasize the fact you love that person, used in both letters and emails. It's often used in love letters actually. And it's indeed the name of a movie - based on a novel (both are really nice).

maybe it's on the end of a talk,and he or she said "and by the way,i love you"

it also means {oh I forgot to tell you}

P.S means {By The Way}, {Just To Let You Know}, or {Don't Forget} P.S is like leaving a simple note behind~ Hope it was helpful~

name of a movie~