On the Internet Super Hero blog, there's a post that looks at how PDO is implemented in PHP and wonders if the PDO::FETCH_UNIQUE constant is broken (as something to fix before even considering the move to PDO2).

I spent quite a lot of time comparing the different behaviours of the various drivers in the hope I could find out how PDO drivers are supposed to work. The PDO documentation and the specification do not cover each and every detail. PDO really needs some love...

He picks out the FETCH_UNIQUE constant as one that needs a little work and tries to track down exactly what it's doing. One issue he found was that it requires combination with other flags to make the unique part of it work correctly (like FETCH_OBJ or FETCH_COLUMN). He works through several examples, both ones that apply the unique call and others that don't, comparing the results.

Dave Dash has posted about a method he developed, using a custom prepend file, to correctly obtain the PATH_INFO information for his server.

symfony and other applications rely on the server's PATH_INFO being set properly. Unfortunately, I use a nonstandard server that doesn't natively support CGI [...] but I can't figure out how to do a urldecode in my configuration.

To get around the issue, he created a file he prepended to each request (via auto_prepend_file) that took the value and urldecoded it to put it in another $_SERVER value.