How to use PHP's Memcache extension?

PHP is a widely used programming language with the advantages of ease of use and efficient performance. In PHP application development, caching technology is usually used to improve application performance. Memcache is a very popular open source distributed memory object caching system. In this article, we’ll cover how to use PHP’s Memcache extension.

Introduction to Memcache extension

Memcache extension is an extension officially provided by PHP, which provides the ability to interact with the Memcache server. Using this extension, we can easily store data into the Memcache server in PHP code, quickly read and update cached data, and improve application performance and response speed.

Before using the Memcache extension, you need to ensure that PHP has installed the extension. You can check whether the Memcache extension is installed by running the following command:

php -m | grep memcache

If the result contains "memcache", the extension is installed. If not, you need to install the Memcache extension first. Taking Ubuntu as an example, use the following command to install:

sudo apt-get install php-memcached

Using the Memcache extension

The Memcache extension provides two ways to connect to the Memcache server:

1. Using the Memcache class

In PHP, you can use the Memcache object to directly connect to the Memcache server to store and read cached data. The following is a simple example:

$memcache = new Memcache;
$memcache->connect('localhost', 11211);

$memcache->set('key_1', 'This is the first value', 0, 60);
$value = $memcache->get('key_1');
echo $value;

$memcache->close();

In the above example, we first create a Memcache object, and then use the connect() method to connect to the Memcache server. ('localhost' and 11211 are the hostname and port number of the Memcache server respectively). After that, we use the set() method to store the key-value pair in the Memcache server and set the expiration time to 60 seconds. Then, use the get() method to obtain the corresponding cache data and output it to the screen. Finally, the close() method is used to close the connection with the Memcache server.

2. Using the Memcached class

After PHP 5.3 version, the Memcached class is provided in the PHP extension to connect to the Memcache server. Its usage method is somewhat different from the Memcache class. The following is an example:

$memcache = new Memcached;
$memcache->addServer('localhost', 11211);

$memcache->set('key_1', 'This is the first value', 60);
$value = $memcache->get('key_1');
echo $value;

$memcache->quit();

In the above example, we create a Memcached object, use the addServer() method to connect to the Memcache server, and then use the set() method to store the key-value pair into the Memcache server , and set the expiration time to 60 seconds. Then, use the get() method to read the corresponding cache data from the Memcache server and output it to the screen. Subsequently, the quit() method is used to close the connection with the Memcache server.

Commonly used functions of Memcache extension

In addition to the above methods of connecting to the Memcache server, Memcache extension also provides some commonly used functions, including:

1. set()

This function is used to store data into the Memcache server. The syntax is as follows:

Memcache::set(string $key , mixed $value [, int $flag [, int $expire ]])

Parameter description:

• $key: the key name of the cache data to be stored;
• $value: the key name of the cache data to be stored Value;
• $flag: optional parameter, used to identify the compression method of stored data, the default value is 0;
• $expire: optional parameter, used to set the expiration time of cached data (Unit is seconds). If this parameter is omitted, cached data never expires.

2. get()

This function is used to read cache data from the Memcache server. The syntax is as follows:

Memcache::get(string $key)

Parameter description:

• $key: The key name of the cached data to be read.

3. delete()

This function is used to delete the specified cache data from the Memcache server. The syntax is as follows:

Memcache::delete(string $key [, int $timeout = 0 ])

Parameter description:

• $key: the key name of the cached data to be deleted;
• $timeout: optional parameter, used for Set the waiting time (in seconds) for deleting cached data. If this parameter is omitted or set to 0, the function returns immediately and cached data is deleted asynchronously in the background. If this parameter is set, cached data will be deleted after timeout seconds.

4. flush()

This function is used to clear all cached data on the Memcache server. The syntax is as follows:

Memcache::flush()

Pay special attention when using this function, because executing this function will clear all cached data on the Memcache server, so use it with caution.

Summary

In this article, we introduced how to use PHP’s Memcache extension and discussed its common functions. By using Memcache extensions, we can easily store data into the Memcache server, speed up the response speed of the application, and reduce the number of accesses to the database, improving the performance and scalability of the application. However, we must also pay attention to ensuring data update and synchronization when using Memcache cache to avoid problems such as data inconsistency.

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