# From PHP 7.1 => PHP 5.6
#Apache
sudo a2dismod php7.1
sudo a2enmod php5.6
sudo service apache2 restart
#command Line
sudo update-alternatives --set php /usr/bin/php5.6//In ubunutu
Default PHP 7.1 is set on your system and you need to switch to PHP 5.6
$ sudo a2dismod php7.1
$ sudo a2enmod php5.6
$ sudo service apache2 restart
sudo update-alternatives --set php /usr/bin/php5.6# Interactive Way
sudo update-alternatives --config phpsudo update-alternatives --config php
sudo update-alternatives --config phar
sudo update-alternatives --config phar.phar
sudo update-alternatives --config phpupdate-alternatives --set php /usr/bin/php7.4
update-alternatives --set phar /usr/bin/phar7.4
update-alternatives --set phar.phar /usr/bin/phar.phar7.4
update-alternatives --set phpize /usr/bin/phpize7.4
update-alternatives --set php-config /usr/bin/php-config7.4