The principles and application scenarios of PHP development cache

The principles and application scenarios of PHP development cache require specific code examples

With the development of Internet technology, PHP has become one of the widely used development languages. In PHP development, the use of cache is a common optimization technology, which can reduce the number of database queries, shorten response time, and improve application performance.

Caching Principle

Cache is a technology that stores data in memory, reducing access to external storage such as disk or database, thereby improving application performance.

The basic principle of caching is to read data from external storage (such as a database or file system) and save it in memory. The next time the data is needed, it can be read directly from the memory, avoiding frequent IO operations on the disk or database.

Since the read and write speed of memory is much faster than that of storage devices such as disks or databases, the use of caching technology can significantly improve access speed and response time.

Application Scenario

In actual applications, cache can be used to read large amounts of data and repeat queries, which can greatly improve response speed and reduce latency. Some typical application scenarios are introduced below.

1. Cache of popular data

Popular data refers to data that is frequently queried, such as the homepage of the website, category pages, etc. These data generally do not change much and are queried frequently. So caching it in memory can save a lot of database query time and network IO time.

For example, the following is an example of PHP code that queries popular sites through the cache:

function getPopularSites() {
    // 先尝试从缓存中读取数据
    $cache = new Memcache();
    $cache->connect('localhost', 11211);
    $data = $cache->get('popular_sites');

    if (empty($data)) {
        // 如果没有缓存，则从数据库中查询数据
        $conn = new mysqli('localhost', 'user', 'password', 'my_db');
        $result = $conn->query('SELECT * FROM sites WHERE visits > 1000');
        $data = $result->fetch_all(MYSQLI_ASSOC);

        // 将数据存储到缓存中
        $cache->set('popular_sites', $data, 0, 3600);
    }

    return $data;
}

The function first tries to read the data from the cache, and if the data is not in the cache, then from the database Query data and store it in cache. The cache is set with an expiration time of 3600 seconds. After expiration, the data will be re-queried from the database.

2. Cache of session data

In PHP applications, session data (Session) is user data saved on the server side. The server must read user data from the disk every time it is requested. . If the application has a large number of users, querying session data will become the performance bottleneck of the server.

In order to speed up the reading of session data, the session data can be cached in memory, such as using caching tools such as Memcache, so that the session data can be read from the memory every time a request is made, without having to read it from the memory every time. Query on disk.

For example, the following is an example of PHP code that uses Memcache to cache session data:

session_start();

function getSessionData($key) {
    // 先尝试从缓存中读取数据
    $cache = new Memcache();
    $cache->connect('localhost', 11211);
    $data = $cache->get(session_id() . '_' . $key);

    if (empty($data)) {
        // 如果缓存中没有该数据，则从会话中读取
        $data = $_SESSION[$key];

        // 将数据存储到缓存中
        $cache->set(session_id() . '_' . $key, $data, 0, 3600);
    }

    return $data;
}

function setSessionData($key, $value) {
    // 将数据存储到缓存和会话中
    $cache = new Memcache();
    $cache->connect('localhost', 11211);
    $cache->set(session_id() . '_' . $key, $value, 0, 3600);
    $_SESSION[$key] = $value;
}

The above code uses session_id() and $key as the cache key value. If there is no data in the cache, Then read from the $_SESSION array and store it in the cache. When the data changes, the data in the cache and $_SESSION array will also be updated at the same time.

3. Caching of data calculation results

In some applications that require frequent calculations, the calculation results can be cached to avoid repeated calculations. For example, paging data, commodity price calculations, etc. These calculations are relatively complex, but in actual use, the same input parameters are likely to be repeatedly calculated in different time periods, so the use of caching technology can greatly improve the efficiency of calculations.

For example, the following is an example of PHP code that uses APC cache to calculate multiplication results:

function multiply($a, $b) {
    // 先尝试从缓存中读取乘法结果
    $result = apc_fetch(sprintf('multiply_%d_%d', $a, $b), $success);

    if (!$success) {
        // 如果缓存中没有结果，则进行乘法计算
        $result = $a * $b;

        // 将计算结果存储到缓存中
        apc_add(sprintf('multiply_%d_%d', $a, $b), $result, 3600);
    }

    return $result;
}

This function caches the calling parameters $a and $b as key values. If there is no data in the cache , the multiplication calculation is performed, and the calculation result is stored in the cache. Each time the function is called, an attempt is made to read the result from the cache to avoid double calculations.

Summary

Caching is a simple and effective optimization technique that can greatly improve application performance and response speed. In PHP development, proper use of caching technology can reduce the number of database queries, shorten response time, and improve user experience.

In actual applications, you can choose different caching tools and caching strategies according to business needs, such as Memcache, APC and other memory caching tools to optimize application performance by caching popular data, session data, calculation results, etc. Purpose.

The above is an introduction to the principles and application scenarios of PHP development cache. It also provides some specific code examples, hoping to be helpful to PHP developers.

The above is the detailed content of The principles and application scenarios of PHP development cache. For more information, please follow other related articles on the PHP Chinese website!