Install PHP development package - CentOS 6 PHP 7.3

Hi I am trying to install the MaxMind DB Reader PHP API C extension. The notes mention that "You may need to install the PHP development package on your OS such as php5-dev for Debian-based systems or php-devel for RedHat/Fedora-based ones." I've tried the install without php-devel but it doesn't work. So I'm looking to install php-devel. I tried: yum install php-devel
which returned : No package php-devel available. Presumably it needs to be installed for the exact PHP version. I'm on CentOS 6, running PHP-FPM with PHP 7.3. So then I Googled the above and it took me here It looks promising but I have no experience installing rpm's and I'm starting to get a bit out of my depth. There are loads of repos out there - the name "remi" comes up often. Can anyone help and tell me where I need to go and what I need to do to install? Thanks