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English
apcu_entry is an advanced interface for cache data in the APCu extension. Its function is to find the specified key in the cache. If the key exists, it returns the corresponding cache value; if it does not exist, data is generated through the callback function and written to the cache, and the data is returned at the same time.
The function prototype is as follows:
mixed apcu_entry ( string $key , callable $generator [, int $ttl = 0 ] )
$key : The key name of the cache entry.
$generator : A callback function that generates cached data (called when the cache does not exist).
$ttl : The cached survival time, unit is seconds, and the default is permanent cache (0).
The traditional cache writing process usually uses apcu_exists to determine whether the cache exists, then calls apcu_fetch to get the cache. If the cache does not exist, then call the function to generate data, and finally write it to the cache. There are race conditions and unnecessary cache access in this process.
Apcu_entry combines query and write processes into atomic operations, avoiding multiple judgments and race conditions, making cached read and write more efficient and safe.
Suppose we have a function to getUserInfoFromDb() to get user information, which is slow to query the database, and hopes to improve performance through cache:
function getUserInfoFromDb($userId) {
// Simulation of time-consuming database query
sleep(2);
return [
'id' => $userId,
'name' => 'user' . $userId,
'email' => 'user' . $userId . '@gitbox.net'
];
}
function getUserInfo($userId) {
$cacheKey = 'user_info_' . $userId;
// use apcu_entry Implement cache management
return apcu_entry($cacheKey, function() use ($userId) {
return getUserInfoFromDb($userId);
}, 3600); // cache1Hour
}
// Call Example
$user = getUserInfo(123);
print_r($user);
In the above example:
When getUserInfo(123) is called for the first time, the cache does not exist. apcu_entry will execute the callback function to obtain data from the database and cache it.
The call then will directly get data from the cache, avoiding duplicate queries.
Set TTL reasonably (survival time)
Set the expiration time of the cache according to the data change frequency to avoid data inaccurate data due to excessive cache.
Avoid cache avalanches <br> Different cache items can set different expiration times to prevent large amounts of caches from expired at the same time causing a surge in database pressure in a short period of time.
Cache breakdown protection
Since apcu_entry is an atomic operation, it can avoid multiple requests to query the database simultaneously, but for more complex scenarios, it can be combined with a lock mechanism.
Cache penetration defense <br> For data that does not exist, it is recommended to cache empty results to prevent malicious or incorrect requests from causing excessive database stress.
apcu_entry is a powerful cache interface in the PHP APCu extension. It simplifies the cache management logic, reduces duplicate queries and competitive problems, and significantly improves the performance of PHP applications.
Reasonable use of apcu_entry , combined with appropriate caching strategies and application scenario design, can significantly improve your PHP applications in response speed and system load.
For more detailed introduction and usage documents of APCu, you can access the official documentation: https://gitbox.net/manual/en/function.apcu-entry.php .
