Implementation and principle of Memcached caching technology in PHP

Memcached is a cache system that is widely used in web servers and other situations where data needs to be cached. In PHP development, Memcached is often used to improve application performance and optimize database access. This article will introduce the implementation and principle of Memcached caching technology.

1. The basic principle of Memcached

Memcached is a cache system that stores key-value pairs in memory. It uses key-value pairs for caching operations, where the key is a unique identifier that distinguishes different data, and the value is the data that actually needs to be cached. Memcached uses hash tables to store and look up key-value pairs, and can perform data lookup, read and write operations at extremely fast speeds.

The main advantage of Memcached is the fast access speed because the data is stored in memory. In addition, because the data is not stored on the hard disk, Memcached is not limited by I/O operations like a traditional database. Since Memcached is a distributed system, it can distribute cached data among multiple servers to achieve high availability.

2. Application of Memcached in PHP

In PHP development, one of the most common applications of Memcached is caching database query results. Generally speaking, when database table data is read frequently, we can use Memcached to cache the data in memory to avoid frequent queries to the database. This can greatly improve the performance and responsiveness of your application.

The application of Memcached in PHP is generally divided into the following steps:

1. Connect to the Memcached server.

The method to connect to the Memcached server in PHP is very simple. Just use the constructor of the Memcached class:

$memcached = new Memcached();

$memcached->addServer('localhost', 11211);

The above code will connect to the Memcached server running on the same host as the current PHP program. If you need to connect to another host, just replace the host name and port number in the above code.

2. Storage cache data.

When storing cached data, you need to specify a unique key value and the data that needs to be cached. For example:

$memcached->set('user_123', ['name' => 'Tom', 'age' => 25]);

The above code will cache A key-value pair named "user_123" whose value is an array containing two attributes: "name" and "age". Whenever you need to get this value, just use this key:

$user = $memcached->get('user_123');

echo $user['name '];

3. Delete cached data.

If you need to delete a key-value pair in Memcached, you only need to use the delete method of the Memcached class:

$memcached->delete('user_123');

4. Refresh the data in Memcached.

When the cache data changes, the cache data needs to be refreshed in time. In PHP, you can use the replace method of the Memcached class to achieve this:

$memcached->replace('user_123', ['name' => 'Jerry', 'age' => 30] );

The above code will refresh the cached data named "user_123", change the value of the "name" attribute from "Tom" to "Jerry", and change the value of the "age" attribute from 25 to 30 .

3. Optimization skills of Memcached

Although Memcached is a relatively efficient and reliable caching technology, in actual applications, you still need to pay attention to some optimization skills to avoid improper use. Caching invalidation or performance degradation.

1. Set cache expiration time.

Memcached can set the expiration time for cached data. Once the cached data expires, Memcached will automatically delete it. In PHP, you can use the setOption method of the Memcached class to set the cache expiration time:

$memcached->setOption(Memcached::OPT_EXPIRATION, 3600); // Set the expiration time to 3600 seconds

2. Use compression algorithm.

Since the data cached by Memcached is usually a long-running operation, it requires a large amount of memory space. To reduce memory usage, compression algorithms can be used to reduce the size of cached data. PHP's Memcached extension integrates a variety of compression algorithms, which can be set by calling the setOption method.

3. Load balancing in a distributed environment.

When Memcached is used in a distributed environment, load balancing is required to ensure that cached data on different servers can achieve balanced distribution and unified management. To achieve load balancing, you can use an algorithm called "consistent hashing" to route requests for the same key value to the same server.

4. Conclusion

This article introduces the implementation and principles of Memcached caching technology, and explains the application and optimization techniques of Memcached in PHP development. By having an in-depth understanding of how Memcached works and how to use it, PHP developers can use Memcached more efficiently and optimally to improve application performance and stability.

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