Ubuntu 16.04 comes with php 7.0, and some php applications might still fail with php 7.0 .Therefore, in some cases, it might be sensible to have both php 7.0 and php 5.x, so that you can choose which version to use for your needs at any time.
You can do so with:
xavi@computer# sudo su
root@computer# add-apt-repository ppa:ondrej/php
root@computer# apt-get update
root@computer# apt-get install php7.0 php5.6 php5.6-mysql php-gettext php5.6-mbstring php-xdebug libapache2-mod-php5.6 libapache2-mod-php7.0 php5.6-curl php5.6-gd php5.6-mcrypt php5.6-xml php5.6-xmlrpc
Installing both php5.6 & php7.0 was clean in my case: no complain of issues, etc.
To switch from php 5.6 to php 7.0 you need to do two things:
# For php in web apps
sudo a2dismod php5.6 && sudo a2enmod php7.0 && sudo service apache2 restart
# For php-cli in the command line
sudo ln -sfn /usr/bin/php7.0 /etc/alternatives/php
or from php7.0 to php5.6:
# For php in web apps
sudo a2dismod php7.0 && sudo a2enmod php5.6 && sudo service apache2 restart
# For php-cli in the command line
sudo ln -sfn /usr/bin/php5.6 /etc/alternatives/php
You can also quickly check which yours is using by running php -v.