I upgraded my office workstation from El Capitan to Sierra last week after waiting a while to make sure there were no problems with the new version of the operating system: my office workstation is used for some campus-wide services, and I go into panic mode when upgrades break things. So after a decent interval it seemed safe to let the upgrade go forward.
It’s a little embarrassing in hindsight how long it took me to recover from the upgrade, but there were no indications whatsoever what had gone wrong: just a cryptic HTTP 500 error code for part of one of the two virtual hosts on the system. Lots of time looking at mail configuration; PHP include_path, etc. Finally: “pg_connect() not found.” I wasn’t getting my “unable to connect to database” error because … postgres wasn’t available at all. The connection couldn’t fail because the code to make the connection couldn’t even be executed.
I’m not the only one to have the problem, of course, and I finally was able to google the correct problem. The solution was simple, just add these two lines to php.ini:
Since I don’t use the PDO interface to Postgres, I probably need only the second line, but I didn’t do the experiment to make sure.
So now I’m back to the old problem: when Apple updates the OS, the path to pgsql.so will undoubtedly change without documentation (that I know of) to alert me to the new path, just as the demotion of Postgres being included in the PHP installation by default was discontinued without documentation (that I know of).