Analysis of persistent storage and recovery strategies for PHP data cache

Persistent storage and recovery strategy analysis of PHP data cache

In PHP application development, data caching is an important optimization method that can significantly improve Application performance and responsiveness. However, in some cases, we need to store cached data persistently so that the data can be restored after an application restart or server restart. This article will introduce some persistent storage and recovery strategies for PHP data cache, and give corresponding code examples.

1. File Storage

File storage is a simple and commonly used persistent storage method, which saves cache data in the form of files on the server's disk. The following is a sample code using file storage:

function cache_get($key) {
    $cache_dir = '/path/to/cache/dir/';
    $file = $cache_dir . md5($key);
    
    if (file_exists($file)) {
        $data = file_get_contents($file);
        $cache = unserialize($data);
        if ($cache['expire'] < time()) {
            unlink($file);
            return false;
        }
        return $cache['data'];
    }
    return false;
}

function cache_set($key, $data, $expire = 3600) {
    $cache_dir = '/path/to/cache/dir/';
    $file = $cache_dir . md5($key);
    $cache = [
        'expire' => time() + $expire,
        'data' => $data
    ];
    $data = serialize($cache);
    file_put_contents($file, $data);
}

In the above code, we use two functions cache_get and cache_set to realize data reading and write operation. cache_getThe function first generates the file name by MD5 encrypting $key, then checks whether the file exists, and if it exists, reads the file content and deserializes it into cached data. Then determine whether the cached data has expired. If it has expired, delete the file and return false. Finally, the cached data is returned. cache_setThe function first generates the file name by MD5 encrypting $key, then saves the cache data and expiration time as an associative array, and serializes the array into a string before writing to the file. Finally, use the file_put_contents function to write the string to the file.

2. Database storage

Database storage is another commonly used persistent storage method, which stores cached data in database tables. The following is a sample code using database storage:

function cache_get($key) {
    $db_host = 'localhost';
    $db_user = 'root';
    $db_password = 'password';
    $db_name = 'cache_db';
    
    $conn = mysqli_connect($db_host, $db_user, $db_password, $db_name);
    if (!$conn) {
        die('Database connection failed: ' . mysqli_connect_error());
    }
    
    $sql = "SELECT data FROM cache_table WHERE `key` = '$key' AND expire >= NOW()";
    $result = mysqli_query($conn, $sql);
    
    if (mysqli_num_rows($result) > 0) {
        $row = mysqli_fetch_assoc($result);
        return $row['data'];
    }
    
    return false;
}

function cache_set($key, $data, $expire = 3600) {
    $db_host = 'localhost';
    $db_user = 'root';
    $db_password = 'password';
    $db_name = 'cache_db';
    
    $conn = mysqli_connect($db_host, $db_user, $db_password, $db_name);
    if (!$conn) {
        die('Database connection failed: ' . mysqli_connect_error());
    }
    
    $expire_date = date('Y-m-d H:i:s', time() + $expire);
    $data = mysqli_real_escape_string($conn, $data);
    
    $sql = "INSERT INTO cache_table (`key`, data, expire) VALUES ('$key', '$data', '$expire_date')";
    mysqli_query($conn, $sql);
}

In the above code, we use two functions cache_get and cache_set to realize data reading and write operation. cache_getThe function first establishes a connection with the database, and then queries whether the corresponding cached data exists in the data table through SQL statements. If data exists in the query results, the value of the data field is returned. The cache_set function first establishes a connection to the database, then obtains the current timestamp plus the date of the expiration time, escapes the data through the mysqli_real_escape_string function, and finally executes an SQL statement to insert the data into the database. table.

3. Memory storage

Memory storage is an efficient persistent storage method. It stores cached data in memory. Even after the application is restarted or the server is restarted, the data can still be recover. The following is a sample code that uses memory storage:

function cache_get($key) {
    $cacheObj = new Memcached();
    $cacheObj->addServer('localhost', 11211);
    
    $data = $cacheObj->get($key);
    return $data;
}

function cache_set($key, $data, $expire = 3600) {
    $cacheObj = new Memcached();
    $cacheObj->addServer('localhost', 11211);
    
    $cacheObj->set($key, $data, $expire);
}

In the above code, we use two functions cache_get and cache_set to realize data reading and write operation. The cache_get function first creates a Memcached object and adds the address and port of the Memcached server through the addServer method. Then use the get method to get the cache data from the memory and return the data. The cache_set function first creates a Memcached object and adds the address and port of the Memcached server through the addServer method. Then use the set method to store the data in memory.

Conclusion

This article introduces the persistent storage and recovery strategy of PHP data cache, including file storage, database storage and memory storage. By choosing the right storage method, you can improve application performance and responsiveness based on actual needs. I hope this article can provide some help to readers in using data caching in PHP application development.

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