Repository installation :

# 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

And, for example, to install PHP 7.3 (alternative streams)

# dnf module install php:remi-7.3
# php --version
PHP 7.3.10 (cli) (built: Sep 24 2019 12:06:35) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.10, Copyright (c) 1998-2018 Zend Technologies

Notice, if you want to install various version simultaneously, the Software Collections of PHP 5.6, 7.0, 7.1, 7.2, 7.3 et 7.4 are also available.

# dnf install php56
# module load php56
# php --version
PHP 5.6.40 (cli) (built: Apr 30 2019 11:08:08) 
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies

 

You can also follow the wizard detailed instructions