php_value include_path in htaccess doesn't work

Hi

I'm trying to set a 'default' include path for the entire site using an
.htaccess file but it doesn't work. The include path always remains the sam
e
and it tells me it can't find the file. The htaccess file is in the root of
the site which is run under apache & Linux. Any idea what I could be doing
wrong?

My .htaccess file is simply this :

php_value include_path /var/www/html/R2/htdocs/includes

Thanks
Chris