Install the packages
/etc/httpd/conf/httpd.conf and make sure you are specifically using the php7 module, it should look like this:
LoadModule php7_module modules/libphp7.so AddHandler php7-script php7 Include conf/extra/php7_module.conf
You shouldn’t need to do anything else besides restart apache:
sudo systemctl restart httpd.
If you need other php extensions install the php 7 version, for example:
sudo pacman -S php7-imagick.
The official arch repos currently only contain php 7 and php 8, but if you need to use any other version, you can install it from the AUR. For example
paru -S php56 /
yay -S php56. The same steps will apply.
Each version of php has it’s own configuration directory. Using php7 as an example: