I noticed that the PostgreSQL function summary does not explain that you need to have configured PHP using --with-pgsql[=DIR]. However, both MySQL and MSQL do. After discovering that I could not use any PostGreSQL functions. I consulted the manual thinking it would tell me that I needed to configure PHP but i didn't. I then looked at MySQL just as a comparison and that did? Something similar to what it says on the MySQL and mSQL pages would, perhaps, avoid confusion in the future.

PS. I added something to this effect to the user contributed notes, however, a rather large URL has meant that it has mucked up the formatting of the page, sorry.