Arch Linux User Repository

When updating your PHP, have a look whether Baikal still works and checkout the comments here for possible issues. Any hints/patches from your side are welcome of course, too. PHP is known to break things and it broke Baikal in the past. At the bottom of this comment you also find NGINX configuration snippets to use an older PHP version. Using an older PHP version is likely the best for being on the safe side although support for older PHP versions is also dropped from time to time from Baikal's side.

All my packages are managed at GitHub where you can also contribute directly: https://github.com/Martchus/PKGBUILDs
There's also a binary repository, also including older PHP versions: https://wiki.archlinux.org/index.php/Unofficial_user_repositories#ownstuff

head -n 20 /etc/nginx/nginx.conf 
[...]
http {
    include php-handler.conf;
    include phpXX-handler.conf;

cat /etc/nginx/php.conf 
location ~ ^(/baikal.+?\.php)(/.*)?$ {
  try_files $1 =404;
  include fastcgi.conf;
  fastcgi_pass phpXX-handler; # handler registered via phpXX-handler.conf included in nginx.conf
  fastcgi_index index.php;
  fastcgi_param SCRIPT_FILENAME $document_root$1;
  fastcgi_param PATH_INFO $2;
  fastcgi_param HTTPS on;
}
location ~ ^(.+?\.php)(/.*)?$ {
  try_files $1 =404;
  include fastcgi.conf;
  fastcgi_pass php-handler; # handler registered via php-handler.conf included in nginx.conf
  fastcgi_index index.php;
  fastcgi_param SCRIPT_FILENAME $document_root$1;
  fastcgi_param PATH_INFO $2;
  fastcgi_param HTTPS on;
}

cat /etc/nginx/phpXX-handler.conf 
upstream phpXX-handler {
  server unix:/run/phpXX-fpm/php-fpm.sock;
}
cat /etc/nginx/php-handler.conf 
upstream php-handler {
  server unix:/run/php-fpm/php-fpm.sock;
}

(XX is of course supposed to be replaced by the actual PHP version.)