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APCu is the successor of APC, Alternative PHP Cache, once its opcode-caching part was superseded by OPcache; only the user-cache API survived under the name APCu.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-liveapcu_fetch()to read a value backapcu_delete()to remove an entryapcu_exists()to check for a key without fetching its valueapcu_inc()/apcu_dec()for atomic countersapcu_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');
?>