update php snippets with 2 useful snips

[developingchris]

2 quick snippets I use a lot.

1 for the newer compressed php tag syntax in codeigniter.
The latter needed when referencing a property on an object, prefixing the call with $this->.

[vsushkov]

vim-snipmate was originally started by Michael Sanders who has now
unfortunately abandoned the project. Rok Garbas is now maintaining a
fork of the project in hopes of improving the existing code base.

[developingchris]

@vsushkov thanks for the heads up, I have actually figured out how to put in user/vendor snips and been satisified with that for now as well.