I had not upgraded my Arch server in a few weeks: ncurses has indeed changed to version 6 as of early September, but PHP should have been upgraded with it.
The quick-n-dirty fix is:
pacman -U /var/cache/pacman/pkg/ncurses-5.9-7-i686.pkg.tar.xz
You can install PHP via
pacman. There'a a number of pieces that I've found necessary, including
php-sqlite. If you're compiling PHP from source to stay at a particular version, I'm not sure that's a good idea as PHP gets patched a lot. It would be hard to keep up with the security patches compiling everything yourself.