Ajax/PostgreSQL

I'm doing some massive (internal company) applications using PHP, which
query extensive PostgreSQL tables. This is fine, but obviously it often
requires multiple web pages to get something done. Supposedly, AJAX
promises to make web pages more interactive. But from what I understand,
I'd have to have bindings from Javascript into PostgreSQL to make this work.

Here's an example: The user wants to enter a bill (accounts payable)
into the system. He first has to pick a vendor. Normally, this would
entail a PHP page that generates a PostgreSQL query. The user would then
get a second page with various vendor information (like number of due
days for that vendor), and various other payable info. But wouldn't it
be nice to have vendor information filled in on the original page,
directly after the user picks a vendor? Theoretically, AJAX might allow
something like this. But from what I can see, it would require
PostgreSQL bindings in Javascript, and some way to pass the data back so
that PHP could use it.

Is this even possible? Is it being worked on? Is there a different
solution I don't know about? I can see where Javascript can alter the
look of a page, but I can't work out how it would allow interactive use
of a PostgreSQL table.

--
Paul M. Foster