CentOS 8

https://www.tecmint.com/install-php-on-centos-8/

Then install these packages:

dnf install php-gd php-ldap php-mysqlnd php-pecl-mcrypt php-pecl-zip

Then remove these packages:

dnf remove php-fpm

CentOS 7

Use this link but substitute in 7.4 for the desired release to activate.

Look at Remi's RPM repository blog

After the install, these PHP packages should be on the system:

php-7.4.33-2.el7.remi.x86_64
php-cli-7.4.33-2.el7.remi.x86_64
php-common-7.4.33-2.el7.remi.x86_64
php-json-7.4.33-2.el7.remi.x86_64
php-mbstring-7.4.33-2.el7.remi.x86_64
php-mysqlnd-7.4.33-2.el7.remi.x86_64
php-pdo-7.4.33-2.el7.remi.x86_64
php-pecl-mcrypt-1.0.5-1.el7.remi.7.4.x86_64
php-sodium-7.4.33-2.el7.remi.x86_64
php-xml-7.4.33-2.el7.remi.x86_64

Remember to merge in local changes to /etc/php.ini