Sometimes, initials can be a problem. My parents didn't consider mine. This lead to me, as a second grader, knocking the top two front (permanent) teeth from a bigger, third-grader's mouth. Needless to say, it wasn't a very popular way to tease me, after that! (If you're not a native English speaker, the "problem" may not be obvious.)
On the subject of shortening, I much prefer "Phil" to "Philip" (American spelling). I'm a very informal person, so my informal name suits me quite nicely!