//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$ sudo update-alternatives --config php
or
$ sudo a2enmod php7.1(version)
update-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
alias setphp="sudo update-alternatives --config php;sudo update-alternatives --config phar; update-alternatives --config phar.phar; a2dismod php*.*;systemctl restart apache2"
Put the above alias in the
sudo nano ~/.bashrc
#After the above command just run this command
a2enmod php<Your Desired Version> # like, a2enmod php7.4
Now you can run command "setphp" from your terminal.