I went ahead and decided to try installing phpBB 3 on PHP 5.3.0RC2 running CGI. The initial build of PHP 5.3.0RC2 went incredibly smoothly, and only a handful of tests failed when I ran `make test.` Got it installed in my web server’s chroot environment and phpinfo runs fine. (After accidentally configuring CGI to use the CLI binary, hehe.)
After that phpBB3 however it gives me the white screen of death when I try progressing into installation. No matter what I do, I can’t seem to get an error message out of it. I’ll try to get some discernibly useful information from it in the coming days. I suspect it’s crashing but the chroot doesn’t have direct access to debug tools, so I may need to set it up elsewhere first.