When viewing PHP scripts with a large number of lines, such as G jumping to the bottom of the file, syntax highlighting is often lost. According to Google, this should be caused by a conflict with the auto-save function. For detailed discussion, see:
Solution , edit .vim/bundle/PIV/ftplugin/php.vim, delete the following lines:
58 call s:InitVariable("g:load_doxygen_syntax", 1)
59 call s:InitVariable("g:syntax_extra_php", ' doxygen')
60 call s:InitVariable("g:syntax_extra_inc", 'doxygen')