Vista backup doesn't backup all files (like for example PHP files)

For some odd reason, the backup tool which comes with windows vista doesn't
backup .php files but store useless files like .php.swp (vi files) or other
useless files in the same directory.

I'm using the file backup tool, and backup it on another HD, once the long
long long process (take more than 3 hours the first time for less than 40Gb),
I checked what was in the backup (with the restore menu), and saw that none
of my PHP files are there.

Moreover, it's a shame we can't define which directory should be backup and
which not as it's storing a lot of files which are useless.