How to implement page caching in PHP?

In web development, page caching is an important technology that can greatly improve website performance and user experience. In PHP, there are many ways to implement page caching. The following will introduce some of the common ones.

1. Use the ob_start() function

The ob_start() function is a function used in PHP to enable output caching. It caches the page output into memory and then outputs the cached content to the browser at the end of the request. Using the ob_start() function can prevent the output content of the page from being displayed temporarily, but cache it first and then output it when it is needed later.

The implementation method is as follows:

<?php
// 开启输出缓存
ob_start();

// 这里书写正常的PHP页面代码
echo 'Hello World!';

// 将缓存的内容输出到浏览器
ob_flush();
?>

You need to pay special attention to the following points when using the ob_start() function:

1. The ob_start() function must be called at the very beginning of the page , otherwise the "Cannot modify header information" error will be thrown.
2. The output cache will occupy the server's memory, and the cache size needs to be set appropriately according to the situation.
3. The cache will not be output immediately. You need to use the ob_flush() function to output the output cache to the browser.

2. Use HTTP caching

HTTP caching is a standard way to implement caching in Web services. It uses Cache-Control and Expires in the HTTP header to control the cache time and Caching strategy. If the page data returned by the server is cached, the next time the client requests the same page, the client will read the data directly from the local cache without having to request the server again, which can greatly improve the access speed of the page.

In PHP, HTTP caching can be achieved by setting Cache-Control and Expires in the response header. Among them, Cache-Control can set max-age, which indicates the effective time of the cache, in seconds. Expires sets the cache expiration time, which is the GMT time of a specified date.

Example of implementation:

<?php
// 设置缓存时间，如下设置了缓存10分钟
header('Cache-Control: max-age=600');

// 设置缓存过期时间，如下设置了缓存到2022年1月1日
header('Expires: Sun, 01 Jan 2022 00:00:00 GMT');

// 这里书写正常的PHP页面代码
echo 'Hello World!';
?>

It should be noted that HTTP caching requires the backend server to return a response header before the browser can cache the page, so it must be used in a PHP file and cannot be used in used in HTML files.

3. Use file caching

File caching is to cache the page to a disk file on the server. When the page is requested again, the file is read directly without parsing by PHP. , which can improve the access speed of the page.

The implementation is as follows:

<?php
// 设置缓存文件名
$cacheFile = 'cache.html';
// 设置缓存时间，如下设置了缓存30分钟
$cacheTime = 1800;

// 如果缓存文件存在并且缓存未过期
if (file_exists($cacheFile) && (time() - filemtime($cacheFile) < $cacheTime)) {
    // 直接读取缓存文件内容
    echo file_get_contents($cacheFile);
    exit();
}

// 开启输出缓存
ob_start();

// 这里书写正常的PHP页面代码
echo 'Hello World!';

// 获取输出缓存并清空缓存
$content = ob_get_clean();

// 把输出缓存写入到缓存文件中
file_put_contents($cacheFile, $content);

// 输出内容到浏览器
echo $content;
?>

In the above code, we first determine whether the cache file exists and whether the cache has expired. If the conditions are met, the content of the cache file is directly output to the browser. If the conditions are not met, the page will be output according to the normal PHP page process, and the contents of the output cache will be written to the cache file.

One thing that needs special attention is that file caching will occupy server disk space. You must set the cache validity period or use scheduled tasks to regularly clean up expired cache files.

To sum up, there are many ways to implement PHP page caching, and each method has its applicable scenarios, advantages and disadvantages. In actual development, it is necessary to make flexible choices based on actual conditions and use caching technology rationally to improve website performance and user experience.

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