How to modify js and css cache within files through php

As the website continues to develop, we often need to update the JS and CSS files in the website. But we all know that browsers have a caching mechanism. As a result, when users browse the website, the new JS and CSS files are not updated, and they continue to use the old files, which will take a long time to be cached in the browser. This Will affect the user experience of the website. So how to solve this problem? Today, this article will introduce how to modify the JS and CSS cache in the file through PHP so that users can use the latest JS and CSS files when visiting the website.

What is cache?

Before introducing how to modify the js and css cache in the file, we must understand what cache is. Caching refers to temporarily saving requested data locally so that it can be accessed more quickly the next time the information is needed. The biggest benefit of caching is that it reduces the load on the server, thereby improving website performance. However, a lack of caching can cause the browser to use expired files instead of the latest versions. That's why we need to modify the js and css cache within the file.

Modify the cache of js and css

However, before modifying the cache of js and css, we need to understand the basic knowledge of HTTP status codes. The HTTP status code is a three-digit numerical code used to tell the client the result of the request. Among them, HTTP 200 means that the request was successful, while HTTP 304 means that your resource has not been updated yet. If we want the browser to use the new JS and CSS files, we need to modify the HTTP status code to tell the browser that the file needs to be requested again every time.

Adding the version number

The first thing we need is to add a version number at the end of the js and css code. When updating, the version number will be changed accordingly, and the browser will re-request the file due to the change in version number. The version number here can be a timestamp or an arbitrarily defined string.

<link rel="stylesheet" href="/css/main.css?v=xxx" type="text/css">
<script src="/js/main.js?v=xxxx"></script>

Modify file cache through php

There are two main ways to modify file cache: through php header information and through htaccess file

Through php header information

php's header() function can set http header information. We can use the header() function to set the http header information of cache-control, pragma (protocol) and expires (absolute expiration time) to tell the browser not to cache. As follows:

// 设置js和css文件不缓存
header('Cache-Control:no-cache,must-revalidate');
header('Pragma:no-cache');
header('Expires:0');

Through htaccess file

htaccess is a configuration file used to configure the Apache Web server. We can modify the cache by modifying the content of the htaccess file. Adding the following code after the .htaccess file will cause the browser to re-request the file:

<IfModule mod_expires.c>
  ExpiresActive on
  ExpiresDefault "access plus 1 year"
</IfModule>

Summary

In this article, we learned what caching is and how to use it through PHP Modify the js and css cache in the file to solve the browser cache problem. We have introduced two methods: modifying the cache through PHP header information and htaccess files. In this way, in the future website development process, we can better solve the caching problem and improve the website's operating efficiency and user experience.

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