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The correct way to refresh the cache using mysqli::refresh

gitbox 2025-05-29

When operating a MySQL database in PHP, you sometimes encounter the problem that cached data is not updated in time. MySQL's caching mechanism can improve query efficiency, but in some cases, we need to force refresh the cache to ensure that the latest data is obtained. The mysqli::refresh function is the tool used to implement this function.

This article will introduce in detail the usage of the mysqli::refresh function, explain how to call it correctly to refresh the MySQL cache, and accompany sample code to help understand.

1. What is mysqli::refresh?

mysqli::refresh is a method provided by the mysqli extension in PHP, allowing developers to refresh the status information and cache of the MySQL server. It corresponds to the FLUSH operation of MySQL, and can refresh various caches, such as table cache, query cache, etc.

2. Function prototype

 public bool mysqli::refresh(int $options)

  • $options : A combination of one or more refresh options, usually using predefined constants.

  • Return value: Return true if the execution is successful, and false if the failure is false .

3. Common refresh options

Here are some constant options supported by mysqli::refresh , which can be used in combination:

  • MYSQLI_REFRESH_GRANT : Refresh permission-related cache.

  • MYSQLI_REFRESH_LOG : Refresh the log file.

  • MYSQLI_REFRESH_TABLES : Refresh the table cache.

  • MYSQLI_REFRESH_HOSTS : Refresh the host cache.

  • MYSQLI_REFRESH_STATUS : Refresh the status variable.

  • MYSQLI_REFRESH_THREADS : Refresh thread cache.

  • MYSQLI_REFRESH_SLAVE : Refresh the information related to the master-slave replication.

  • MYSQLI_REFRESH_MASTER : Refresh the main server related information.

  • MYSQLI_REFRESH_QUERY_CACHE : Refresh the query cache.

4. Sample code: Refresh query cache

The following example shows how to connect to a MySQL database and refresh the query cache:

 <?php
$mysqli = new mysqli("gitbox.net", "username", "password", "database");

if ($mysqli->connect_errno) {
    echo "Connection failed: " . $mysqli->connect_error;
    exit();
}

// Refresh query cache
if ($mysqli->refresh(MYSQLI_REFRESH_QUERY_CACHE)) {
    echo "Query cache refresh successfully";
} else {
    echo "Query cache refresh failed: " . $mysqli->error;
}

$mysqli->close();
?>

The MYSQLI_REFRESH_QUERY_CACHE option is used here to refresh the MySQL query cache.

5. Combining multiple refresh options

If you want to refresh multiple caches at the same time, you can pass constants using bitwise or operators | combination:

 $mysqli->refresh(MYSQLI_REFRESH_TABLES | MYSQLI_REFRESH_QUERY_CACHE);

This code will refresh the table cache and query cache.

6. Things to note

  1. Permissions issue : The operation to refresh the cache usually requires administrator privileges (such as RELOAD privileges), otherwise the execution will fail.

  2. Cache refresh cost : Frequent refresh of cache may affect database performance and is recommended to use it if necessary.

  3. Scope of application : mysqli::refresh is mainly used in scenarios that require manual control of cache refresh, such as development and debugging or operation and maintenance scripts.

By using the mysqli::refresh function rationally, PHP developers can control MySQL cache refresh more flexibly to ensure data consistency and up-to-dateness.

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