The Alternative PHP Cache (APC) is a free and open opcode cache for PHP
OPcache is a PHP opcode cache introduced in PHP 5.5 (and is also available as a PECL extension for PHP 5.2+)
"I am using yii 1.1.12 and recently upgraded my php from 5.3 to 5.5 and have found that apc is no longer to be used because opcache has been made part of php5.5"
from question "Yii 1.1.12 : How to confiure OpCache : I upgraded PHP from 5.3 to 5.5"
"Zend opcache appears to be more performant than apc more fully featured and more reliable"
from question "Are Zend Server's OPcache and PHP's OPcache the Same Thing?"
"I don t want to use apc because opcache is around 10 faster than apc"
from question "Installing php5.3 with Opcache"