我在PHP应用程序中是否正确地支持UTF-8 ?

I would like to make sure that everything I know about UTF-8 is correct. I have been trying to use UTF-8 for a while now but I keep stumbling across more and more bugs and other weird things that make it seem almost impossible to have a 100% UTF-8 site. There is always a gotcha somewhere that I seem to miss. Perhaps someone here can correct my list or OK it so I don't miss anything important.I would like to make sure that everything I kno