CentOS 8

sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-Linux-* 
sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-Linux-*

dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
dnf install https://rpms.remirepo.net/enterprise/remi-release-8.rpm

yum 인스톨해도 진행은 됩니다 (글쓴이는 yum으로 설치)
yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
yum install https://rpms.remirepo.net/enterprise/remi-release-8.rpm -y

dnf module reset php
dnf module install php:remi-7.4

yum 설치 가능
yum module reset php
yum module install php:remi-7.4

yum update php

http://YourServerAddress/phpinfo.php

Good Luck To You^^

Thank You!!