Why does php not respond when modifying css?

In website development, PHP and CSS are two very important technologies. PHP is mainly responsible for the business logic and data processing of web pages, while CSS is responsible for the style presentation of web pages. In actual development, we often encounter situations where PHP modifies CSS styles but does not take effect. So why does this happen?

1. Caching problem

In order to speed up the loading of web pages, the browser will cache some static resources of the web page, so that the user can read directly from the cache the next time he visits the same page. Get resources without re-requesting the server. However, if PHP modifies the CSS style, the old style will be cached by the browser, causing the new style to fail to take effect. There are many ways to solve this problem. The simplest way is to add a version number or timestamp (such as style.css?v=1) to the link to the CSS file, so that the browser will know that the resource has been updated, thus Reload new styles.

2. CSS priority issue

The display effect of CSS styles is determined based on priority. Depending on the characteristics of CSS selectors, the same element may have multiple CSS style rules acting on it. In this case, the issue of CSS priority arises. Generally, the priority order of CSS styles is: inline style > ID selector > Class selector > Tag selector. If PHP modifies a CSS style, but the priority of the style is lower than the defined style rule, the modification will not take effect. To solve this problem, you can override the previously defined style rules by using a higher priority selector.

3. Syntax error

PHP modification of CSS style cannot take effect, which may also be caused by syntax errors. If there is a syntax error when modifying the CSS style, the browser will not be able to parse the CSS file correctly, causing the style to not be displayed normally. At this point, we need to check the CSS file for syntax errors.

4. Force refresh problem

Sometimes after PHP modifies the CSS style, the browser still cannot display the new style correctly. At this time, we can try to force refresh the page. Force refresh can clear the browser's cache and reload static resources to ensure that the new style takes effect. Usually, we can use the shortcut key "Ctrl F5" to force refresh the page.

To sum up, when modifying CSS styles in PHP does not take effect, we need to check possible reasons such as cache issues, CSS priority issues, syntax errors and forced refresh issues, and then take appropriate measures to solve this problem. question.

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