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English
APCu is a cache system used in PHP to accelerate data reading. It can store data in shared memory and reduce database access. apcu_entry is an advanced function provided by APCu. It combines cache write and read operations to ensure that data can be read efficiently when it exists in the cache.
The working mechanism of apcu_entry is: if there is a corresponding value in the cache, it will directly return this value; if not, it will obtain the value through the callback function and store the value in the cache. This mechanism is very suitable for scenarios where you need to compute or get from an external data source (such as a database).
The paging function is usually used to display large amounts of data, split the data into multiple small pieces for display. A typical scenario of paging query is when a user requests data from a certain page, the system querys the data of that page from the database. Every time the user switches the page, the database will be requeried, causing unnecessary performance waste.
We can use the apcu_entry function to cache the paged data to avoid querying the database every time. When the user requests data, first check whether the page data exists in the cache. If it exists, directly return the cached data, otherwise query the database and cache the results.
Here is a simple example that demonstrates how to cache paging data through apcu_entry :
<?php
// Simulate database query function
function getDataFromDatabase($page, $limit) {
// Assume every page 10 Data
$start = ($page - 1) * $limit;
$end = $start + $limit - 1;
// Simulate database data（In actual situations, data should be queried from the database）
$data = [];
for ($i = $start; $i <= $end; $i++) {
$data[] = "Item " . ($i + 1);
}
return $data;
}
// Functions to get paginated data
function getPaginatedData($page, $limit = 10) {
// Constructing a cache's unique key
$cacheKey = "page_{$page}_limit_{$limit}";
// use apcu_entry Cache data
$data = apcu_entry($cacheKey, function() use ($page, $limit) {
// If there is no data in the cache，Query the database
return getDataFromDatabase($page, $limit);
}, 3600); // cache 1 Hour
return $data;
}
// use示例：Get the first 2 Page data
$page = 2;
$data = getPaginatedData($page);
echo "Page $page data:\n";
print_r($data);
?>
getDataFromDatabase : simulates a function to obtain paging data from the database. In actual applications, it can be replaced with a real database query operation.
getPaginatedData : This function uses apcu_entry to cache paginated data. It constructs a cache key based on the page number, and returns it directly if there is data in the cache; if there is no data in the cache, the callback function is called to obtain data from the database and store the data in the cache.
The use of apcu_entry : the first parameter is the cached key, the second parameter is the callback function, which is used to obtain data, and the third parameter is the cached expiration time (in seconds). In this case, the data will be cached for 1 hour.
Reduce database queries : If the paginated data has been cached, there is no need to repeatedly query the database, which reduces the burden on the database.
Improve response speed : Cache can greatly improve read speed and reduce calculation and database access every request.
Simple and easy to use : Cache can be easily implemented through apcu_entry , with concise code and high performance.
Cache Cleanup : The data in the cache is not always valid. A reasonable expiration time should be set according to business needs, or the cache should be cleaned manually.
Memory management : APCu uses shared memory. In highly concurrent applications, memory usage and cleaning strategies need to be considered to avoid system performance problems due to excessive cache memory usage.
Cache consistency : The data in the cache and database need to be consistent. If the data in the database changes, the cache should be cleaned in time to avoid returning expired data.
