undefined query!!!!!

dear all

I've subscribed in the hope of a simple answer to my dilemma.
I run a dev box(mandrake) with php4 and postgres fine
I just added postgres support using apt-get on my debian production box
after restarting apache I get this

Fatal error: Call to undefined function: pg_query()
when I try to query?

this was added to my php.ini
extension=pgsql.so

and I checked it exists
can anyone help?
have i given enough info


James