Install all the necessary repos and packages

The following commands assume you already sudo su - or you will have to add sudo to each of the commands:

yum install httpd -y
yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
yum install http://rpms.remirepo.net/enterprise/remi-release-7.rpm
yum install yum-utils -y
yum install php56 -y
yum install php72 -y
yum install php56-php-fpm -y
yum install php72-php-fpm -y

Stop both fpm servers

systemctl stop php56-php-fpm
systemctl stop php72-php-fpm

By default it listens on 127.0.0.1 port 9000, make them listen on different ports

sed -i 's/:9000/:9056/' /etc/opt/remi/php56/php-fpm.d/www.conf
sed -i 's/:9000/:9072/' /etc/opt/remi/php72/php-fpm.d/www.conf

Now two different version of fpm can be started on different ports

systemctl start php72-php-fpm
systemctl start php56-php-fpm

make script wrapper to call php56-cgi and php72-cgi

cat > /var/www/cgi-bin/php56.fcgi << EOF
#!/bin/bash
exec /bin/php56-cgi
EOF

cat > /var/www/cgi-bin/php72.fcgi << EOF
#!/bin/bash
exec /bin/php72-cgi
EOF

Make them executable by apache

sudo chmod 755 /var/www/cgi-bin/php56.fcgi
sudo chmod 755 /var/www/cgi-bin/php72.fcgi

Create php configuration for apache. by default it runs php56-fcgi handler

cat > /etc/httpd/conf.d/php.conf << EOF
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"
AddHandler php56-fcgi .php
Action php56-fcgi /cgi-bin/php56.fcgi
Action php72-fcgi /cgi-bin/php72.fcgi

<Directory /var/www/html/php56>
    DirectoryIndex index.php
    AllowOverride all
    Require all granted
</Directory>
<Directory /var/www/html/php72>
    DirectoryIndex index.php
    AllowOverride all
    Require all granted
</Directory>
EOF

Make test pages, create .htaccess to use php72-fcgi

mkdir -p /var/www/html/php56
mkdir -p /var/www/html/php72
echo "<?php phpinfo(); ?>" > /var/www/html/php56/index.php
echo "<?php phpinfo(); ?>" > /var/www/html/php72/index.php
echo "AddHandler php72-fcgi .php" > /var/www/html/php72/.htaccess

Now you should be able to test it

(http://127.0.0.1/php56)
(http://127.0.0.1/php72)

If you want to startup these instance automatically after server reboot

sudo systemctl enable httpd
sudo systemctl enable php56-php-fpm
sudo systemctl enable php72-php-fpm