How to control cache expiration time in PHP?

With the popularity of Internet applications, website response speed has become more and more of a focus for users. In order to quickly respond to user requests, websites often use caching technology to cache data, thereby reducing the number of database queries. However, cache expiration time has an important impact on response speed. This article will discuss methods of controlling cache expiration time to help PHP developers better apply caching technology.

1. What is cache expiration time?

The cache expiration time refers to the time when the data in the cache is considered to have expired. It determines when the data in the cache needs to be updated. In most cases, the data in the cache should expire after a certain period of time to ensure that the data in the cache remains in sync with the source data.

2. Why should we control the cache expiration time?

The purpose of controlling the cache expiration time is to ensure that the data in the cache does not become outdated, thereby ensuring the website response speed. Expired cached data may cause a decrease in cache hit rate and increase the load on the server.

3. Methods to control cache expiration time

1. Set expiration time

When using memcache cache, you can control the cache expiration time by setting the expiration time. For example:

$key = 'user:1';
$val = $memcache->get($key);
if ($val === false) {
    $val = db_query('SELECT * FROM user WHERE id = ?', $id);
    $memcache->set($key, $val, MEMCACHE_COMPRESSED, 3600); //设置过期时间为3600秒
}

In this code, the fourth parameter of the memcache->set() function indicates the validity period of the cached data, in seconds.

2. Use automatic expiration cache

Automatic expiration cache means that when the cached data expires, the cache is automatically updated from the source data. This method requires setting a cache automatic expiration time when using cache. When the cache time expires, the cache will be automatically updated from the source data at the next cache request. For example:

$key = 'user:1';
$val = apc_fetch($key, $success);
if (!$success) {
    $val = db_query('SELECT * FROM user WHERE id = ?', $id);
    apc_add($key, $val, 3600); //设置过期时间为3600秒
}

In this code, after the apc_add() function sets the cache time, after the cache expires, if the cache no longer exists, the cache will be automatically updated from the source data.

3. Use OPcache

OPcache is an extension of PHP that can cache compiled PHP scripts. After OPcache is enabled, PHP scripts will only be compiled and interpreted once, and the compiled results are cached in memory, thus improving the execution efficiency of PHP code. The cache expiration time of OPcache is determined by the parameters in the OPcache configuration file. For example:

[opcache]
opcache.enable=1
opcache.enable_cli=0
opcache.memory_consumption=128
opcache.interned_strings_buffer=8
opcache.max_accelerated_files=4000
opcache.revalidate_freq=60
opcache.fast_shutdown=1
opcache.enable_file_override=0

The opcache.revalidate_freq parameter in this configuration file indicates how long the cached data needs to be re-validated, and determines the cache expiration time of OPcache.

4. Summary

Controlling cache expiration time is one of the skills that PHP developers must master. In actual applications, developers need to choose appropriate caching technology and select an appropriate cache expiration time based on application scenarios and requirements. At the same time, it is also necessary to clean and update the cached data of the application regularly. By rationally using caching technology and controlling cache expiration time, we can improve the response speed of the website and improve the user experience.

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