Vim ignores shiftwidth specified in .vimrc

Question

I am using Vim 7.3.154 cli on Linux Mint 12 "Lisa"(x64).

I prefer using a tabstop and shiftwidth of 2 columns. My .vimrc has
:set ts=2
:set sw=2
to accomplish the same.

Whenever I open a new instance of Vim, tabstop value is retained, so existing tabs are rendered according to .vimrc. But somehow the shiftwidth value gets changed to 3. This results in 3 column indention while auto-indenting.
Running :set sw=2 on the new instance of Vim fixes this issue.
Can anyone tell me why Vim is ignoring/changing shiftwidth value from .vimrc?

I tried disabling all plugins to no avail.

Vim compiled options | .vimrc

Answer 1

This answer just summarizes what we discussed in the comments. :)

This is most likely caused by the fact that you have file specific settings enabled. Check :h modeline for more info on that. Make sure that those files you have the problems with don't have this line in them.

---

Instead of only setting tabstop and shiftwidth you should also setup a couple more settings regarding whitespace and tabs.

set noexpandtab " Make sure that every file uses real tabs, not spaces
set shiftround  " Round indent to multiple of 'shiftwidth'
set smartindent " Do smart indenting when starting a new line
set autoindent  " Copy indent from current line, over to the new line

" Set the tab width
let s:tabwidth=4
exec 'set tabstop='    .s:tabwidth
exec 'set shiftwidth=' .s:tabwidth
exec 'set softtabstop='.s:tabwidth

Check this video for some extra info: http://vimcasts.org/episodes/tabs-and-spaces/

---

So this is the answer to the actual problem that you were able to solve. That php.php file was in the /plugin directory. That directory gets loaded once, each and every time Vim starts up. Check this: http://learnvimscriptthehardway.stevelosh.com/chapters/42.html#vimplugin

If what you want is that file to load only on PHP files then you should put it in the /ftplugin folder: http://learnvimscriptthehardway.stevelosh.com/chapters/42.html#vimftplugin

Read the documentation there, it should be a .vim file, in other words in this case it would be called php.vim.

What Pathogen or Vundle do is modify the runtimepath (:h runtimepath), nothing more, nothing less.

So you can now accept this answer, by clicking the little green arrow to the left of this answer. :)