Install PHP 7.1 on CentOS 8.3

Solution 1:

PHP 7.1 is EOL and no longer supported. If you absolutely must have it, the only option left to you would be to try and build it from source.

This is a decent guide to follow for building it from source - I quickly ran through it on a CentOS 8 VM and was able to get PHP compiled and installed, though I did notice a few warnings it barked about along the way, which could cause some unknown issues post-install. I had to add some additional installations at the install step, like so: dnf autoconf libtool bison libxml2-devel bzip2-devel libcurl-devel libpng-devel libicu-devel gcc-c++ libmcrypt-devel libwebp-devel libjpeg-devel make freetype-devel httpd httpd-devel perl.

I would highly recommend installing a newer, support version via Remi Repos. I followed this guide and was able to install 7.4 without issues. It also has 7.2 available as well, which depending on your needs for 7.1 may be an easier solution, though I believe 7.2 is unsupported now as well.