I created 2 project on the same server.
Project-1:
    $frontCache = new \Phalcon\Cache\Frontend\Data(array(
            "lifetime" => 86400
    ));
    $cache = new \Phalcon\Cache\Backend\Apc($frontCache, array(
            'prefix' => 'prefix-1-'
    ));Project-2:
    $frontCache = new \Phalcon\Cache\Frontend\Data(array(
            "lifetime" => 86400
    ));
    $cache = new \Phalcon\Cache\Backend\Apc($frontCache, array(
            'prefix' => 'prefix-2-'
    ));Both Project-1 and Project-2 save a cached object the same key but with different value.
When I open both projects the cached object have the same value. It seems that APC use no prefix.
Thanks for the help!