APCu

APCu, APC User Cache, is a PHP extension that provides a shared-memory, in-process key-value store for caching arbitrary data between requests, without needing an external service like Memcached or Redis.

APCu is the successor of APC, Alternative PHP Cache, once its opcode-caching part was superseded by OPcache; only the user-cache API survived under the name APCu.

Common functions include:

• apcu_store() to write a value, with an optional TTL, time-to-live

• apcu_fetch() to read a value back

• apcu_delete() to remove an entry

• apcu_exists() to check for a key without fetching its value

• apcu_inc() / apcu_dec() for atomic counters

• apcu_clear_cache() to flush the whole cache

Because the cache lives in shared memory local to the PHP process pool, it is fast, but it is not shared across servers; in a multi-server, load-balanced setup, a distributed cache such as Redis or Memcached is usually preferred.

<?php

    if (apcu_exists('user_count')) {
        $count = apcu_fetch('user_count');
    } else {
        $count = count_users_from_database();
        apcu_store('user_count', $count, 300); // cache for 5 minutes
    }

    apcu_inc('page_views');

?>

Documentation

See also PHP manual: APCu.

Related : Shared Memory, Opcache, Cache, , , Session