I went through this when writing up the install documentation. I THINK the problem here is that Ubuntu 16.04 defaults to php7 and OpenCATS will not work with php7 yet.
I solved this by downgrading php to 5.6.
Here are condensed instructions from the following tutorial:
http://askubuntu.com/questions/761713/h ... untu-16-04
1. Re-Install PHP 5.6
What worked for me was this guide:
http://www.lornajane.net/posts/2016/php ... -on-ubuntu
Actually is not required to remove php7.0, you can install php5.6 together ( also because you will have dependency problem with phpmyadmin package that required php7.0)
Assuming libapache2-mod-php is a suitable way to enable PHP in Apache for you, you can proceed in this way:
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo 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
2. Switch PHP version:
from php7.0 to php5.6:
Apache:
sudo a2dismod php7.0 ; sudo a2enmod php5.6 ; sudo service apache2 restart
CLI:
sudo ln -sfn /usr/bin/php5.6 /etc/alternatives/php
Make sure when you install the php extension after, that you install and use the 5.6 extentions (ex php5.6-mysql).
Please post if there are any additional issues...