php-apcu-bc package provides a backwards compatibility layer from apcu -> apc, and is reuqired for some older PHP code bases (e.g. Yii 1). The package is not (yet) available in the Ubuntu 16.04 repos. To install it, use php-pear:
sudo apt-get install php-dev php-pear sudo pecl install apcu_bc-beta
/etc/php/7.0/apache2/php.ini and add the following at the end of the file:
[apcu] extension=apcu.so extension=apc.so apc.enabled=1
The order is important here!
apcu.so has to be included before