Mysql may be on the box, but is php compiled to use mysql?
If you look in your apache libexec directory (or whereever your php module is living (httpd.conf)) - do the following:
dump -C libphp4.so | grep -i mysql
If you don't see any mysql functions, your PHP wasn't compiled with mysql support (ie
In PHP src directory (php-4.0.3pl1/)
# ./configure --with-mysql \
--with-xml \
--enable-track-vars \
--with-apache=../apache_1.3.14 \
# make
# make install
Cheers,
Keith