Is pgsql threadsafe?

Hi all,

Last week I found the php_pgsql extension wouldn't work on IIS6,
windows server 2003, using php isapi. PHP was running fine, and I'm
99% certain the extension was loaded, extension_loaded() returned true
and a call to pg_connect produced no error messages, but no connection
either. No error messages were produced at all.
When the extension was not loaded I got the usual pg_connect()
undefined message.

I eventually got it running using fastcgi - which can run
non-threadsafe php on multithreaded web servers.

Is php_pgsql threadsafe?  Is this usual behaviour?  In which case I'm
going to abandon pgsql for pdo - I thought I was going to have to
rewrite my entire application about 3 days from the deadline 'til it
worked (hours of hair-tearing later) with fastcgi.

Thanks

Will