GVim, Vim, Indexer How-to indexing

Just found out that my Vim indexer.vim only starts to indexing or re-indexing if i start my gvim
from command line under the my web application project directory.

option:ctags_params=" --exclude='*.sql' --exclude='*.js' --exclude='*.css' --PHP-kinds=+cf --fields=+iaS --extra=+q --regex-PHP='/(abstract class |class ) ([^ ]*)/\\1/c/' --regex-PHP='/interface ([^ ]*)/\\1/c/' --regex-PHP='/(public |static |abstract |protected |private )+function ([^ ()]*)/\\2/f/' --regex-PHP='/define[(].([a-zA-Z0-9_]*)/\\1/f/' "

Indexer starts to running ctags at background process if i start gvim from /opt/lampp/htdocs/sc just like
the [sc] rule. Why bother? Well i noticed from my past experience is that ctags or re-indexing will be
started if i open one of my file under [sc] rule, which is /opt/lampp/htdocs/sc, and indexer would picked
up and re-indexing. Indexer smart enough to check if a file is open from any rules that supplied in

But anyway luckly i found out that the re-indexing or indexing could be performed at the directory
of the rule (project) specified in .indexex_files file. Any thought?

Indexer does indexing if i open a file of any project that specified in .indexer_files and if only if
this is  the first file of first tab.

I usually work with multiple tab, thus any project that opened in new tab any file that opened will
no longer triggers indexer to re-indexing. For each tab i use NERDTree to have this beautiful
left navigations of a folder which is my project tree.