Well, there is an install forum here, but it doesn't get read too much. I don't know that you'd have better luck there.
That said, there's a FAQ there for Linux. I've not read it, I've had no problems installing PHP.
You might try the manual http://us2.php.net/manual/en/install.unix.php for general information on the ./configure make make install method (old-style??) building of PHP/Apache/MySQL, whatever.
The PHP manual helped me set up my first install of PHP on FreeBSD. Since that time I use the FBSD ports system ... set and forget, mostly. I'd say you'll have to do it the old way, but I no nothing about AIX, except it's another flavor of 'Nix.
So, um PERL forums are nicer? :eek: If you bash PERL here, you usually get a chorus of AMENs and two or three very hot flames ... and a few youngsters who say, "didn't PHP come from PERL?"
HTH, 😉