PHP Vim autocomplete

I can not get the autocomplete to work for php files. I added the following to my .vimrc file but when I type c开发者_如何学Pythontl + o nothing happnens. When I type ctl + x i get -- ^X mode (^]^D^E^F^I^K^L^N^O^Ps^U^V^Y) at the bottom of vim.

filetype plugin on
autocmd FileType php set omnifunc=phpcomplete#CompletePHP

---

What you probably want is Ctrl + xCtrl + o in succession.

Incidentally, I map this to Ctrl + Space so as not to feel like I'm using Emacs.

---

I think you want ^P, but I'm not sure.