Don't leave trailing whitespace when text wrapping

First asked on https://groups.google.com/forum/#!topic/vim_dev/Q_KGrMevqW0 and was told the error was with the indent/php.vim script and to contact its maintainer, which I have done here.

Trailing whitespace is left at the end of comment lines when text is wrapped as a result of the 'textwidth' setting. This only occurs in the PHP filetype.

Removing formatoptions+=w fixes the bug, as done in this pull request.