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English
apcu_entry is a caching mechanism provided by the apcu extension in PHP, which is used to store and retrieve data in PHP applications. It is a user cache component of the APC (Alternative PHP Cache) extension. APC extensions provide an efficient user-level caching system designed to store variables and objects and keep them in memory, reducing the overhead of multiple calculations.
Unlike common APC or apcu_cache related functions, apcu_entry is a cache entry with an automatic expiration mechanism. Through apcu_entry, developers can set the cached survival time (TTL, Time To Live), that is, how long it takes to automatically fail, thereby ensuring the timeliness of data.
Here is a simple example showing how to use apcu_entry for caching:
<?php
$key = 'user_data';
$data = array('name' => 'John', 'age' => 30);
// Set cache entries
apcu_entry($key, $data, 3600); // cache 1 Hour
// 获取cache条目
$cachedData = apcu_fetch($key);
if ($cachedData) {
echo '数据来自cache：' . print_r($cachedData, true);
} else {
echo 'cache过期或未设置cache。';
}
?>
In this example, use apcu_entry to store the data in memory and set its expiration time to 3600 seconds (i.e. 1 hour). If the cache has not expired, the data is retrieved directly from memory; if it has expired, the data is recalculated.
apcu_entry : APCU mainly stores data in the local memory of the PHP application server, so it is a local cache system. Each application instance has an independent cache space and data is not shared. When a PHP application runs on multiple servers, the APCU cannot share data across servers.
Redis : Redis is an in-memory database system that supports persistence and is usually used as a distributed cache. Redis is a distributed cache system, whose data is stored in an external server (such as a Redis server), and can share data between multiple application instances, suitable for caching requirements across servers.
apcu_entry : APCU is a non-persistent cache. When the PHP process restarts, data in the APCU is lost. Therefore, it is usually suitable for storing some temporary data or short-term cache.
Redis : Redis offers multiple persistence options, such as RDB snapshots and AOF logs, which means that data in Redis can be restored upon server restart. Redis is better suited to storing data that needs to be kept for a long time.
apcu_entry : Since the APCU is based on local memory, cached data can only be shared in a single server instance, and data cannot be shared across multiple server instances. Therefore, APCU is more suitable for stand-alone environments.
Redis : Redis is a distributed cache system that can share cached data across multiple servers. Redis is an ideal choice for large applications that require horizontal scaling.
apcu_entry : APCU operates directly in PHP process memory, so it has very fast access speed. For simple caching requirements, APCUs have high performance and low complexity.
Redis : Although Redis is also very fast, it has slightly slower access speeds compared to APCUs because it requires communication with external Redis servers over the network, especially in high concurrency scenarios, network latency may become a performance bottleneck. However, Redis provides rich data structures and more features, suitable for more complex cache scenarios.
apcu_entry : suitable for stand-alone environments, storing fast access data, especially for PHP applications without distributed requirements. It is often used to cache database query results, session data, etc.
Redis : suitable for scenarios where cached data needs to be shared across multiple application instances and across multiple servers. Redis is suitable for advanced features such as cache large data sets, persistent data storage, and even message queues.
