The difference and combination of apcu_entry and apcu_store

The apcu_store function is used to store data into the APCu cache. Its basic usage is as follows:

 apcu_store('key', 'value');

Here 'key' is the key of the cache item, and 'value' is the data we want to cache. This function will save the data to the APCu cache so that it can be accessed quickly in the future. apcu_store is a mandatory storage operation that directly overwrites the original value even if the key already exists.

apcu_store can also accept additional parameters such as TTL (survival time). For example:

 apcu_store('key', 'value', 3600); // Data storage for one hour

This will store the data and set the expiration time to 3600 seconds (i.e. 1 hour). However, this function does not determine whether the key's data is already in the cache, it will directly store or update the existing data.

2. apcu_entry function

Compared with apcu_store , the apcu_entry function is more intelligent. Its purpose is to check whether a key already exists in the cache. If the key does not exist in the cache, a new value will be calculated and stored. If the key already exists, the value in the cache is returned directly without recalculating.

The basic usage of apcu_entry is as follows:

 $value = apcu_entry('key', function() {
    // Calculate or get data
    return 'computed value';
});

In this example, apcu_entry will first check if 'key' exists. If present, it will directly return the value in the cache. If it does not exist, it executes the callback function, calculates the value, and stores the result in the APCu cache.

This method avoids repeated calculations, especially when the calculation process is complex or time-consuming, it can effectively improve the efficiency of the program.

3. The difference between apcu_entry and apcu_store

Storage method

• apcu_store directly stores the data into the cache and overwrites the original data.

• apcu_entry first checks whether there is data in the cache. If not, the data is calculated through the callback function and stored in the cache.

Use scenarios

• apcu_store is suitable for scenarios where cached data needs to be stored or updated directly.

• apcu_entry is suitable for scenarios where data is calculated only when the cache does not exist, and avoids repeated calculations.

Performance optimization

• apcu_entry can effectively avoid repeated calculations, especially when complex calculations or queries are required, it can reduce unnecessary load.

• Although apcu_store is simple and direct, it may cause performance problems if the data needs to be recalculated when the cache does not exist.

4. How to use these two functions in combination?

In order to maximize the cache usage effect, apcu_entry and apcu_store can be combined to achieve efficient data cache management.

Sample code:

Suppose we have a data that needs to be queried from the database and we want to cache the query results. If the cache does not exist, query and cache the results; if the cache already exists, use the cache directly.

 $key = 'user_data_' . $userId;

// useapcu_entryTry to get cached data，If it does not exist, then
$data = apcu_entry($key, function() use ($userId) {
    // Simulate database query operations
    return get_user_data_from_db($userId); 
});

// In some cases，可以useapcu_storePerform explicit cache updates
if ($data['updated']) {
    apcu_store($key, $data);
}

In this example, apcu_entry checks if the cache already has the specified key, and if not, it executes a database query and caches the result. With apcu_store , we can explicitly overwrite the cache if the data needs to be updated.