php-apcu 5.1.19+4.0.11-3build1 (amd64 binary) in ubuntu impish

 The APCu is userland caching: APC (Alternative PHP Cache) stripped of
 opcode caching after the deployment of Zend OpCache in PHP 5.5 as the
 primary solution to opcode caching in future versions of PHP.
 .
 The APCu is a fast solution for userland caching (and dumping) of PHP
 variables locally, it is not distributed like MemcacheD, but they can
 be used together for optimal caching.