tracker does not index .php files content

Binary package hint: tracker

Hi,
I am using Ubuntu 10.10 and Tracker 0.8.17, and realized that Tracker does not index .php files content (it is useful to me when searching for the place a function name is used).

Activating the tracker-extract log, I can read :
>>> Could not find any extractors to handle metadata type (mime: application/x-php) <<<

In /usr/lib/tracker-0.8/extract-modules directory is a list of extractors modules, like : libextract-html.so, libextract-text.so, libextract-pdf.so, etc... but there is nothing specific for php files.

Does application/x-php files need a specific extractor ?
I was expecting that .php files, because they contain plain-text (PHP script text), would be indexed as well.

Couldn't the libextract-text.so applies to such mime types as well ?
I can see in libtracker-extract page on the wiki (http://library.gnome.org/devel/libtracker-extract/unstable/libtracker-extract-How-to-use-libtracker-extract.html) that several MIME types can be defined for the same lib.

Or is it required to create a new specific extractor ? (which is out of my knowledge)

Thank you.