PHP Regular Expressions: How to match all stylesheet links in HTML

In HTML, style sheet links are usually embedded within the head tag. These links point to CSS files that contain style rules that customize the display of the document.

In some cases, we need to write code to automatically process HTML pages, such as removing or replacing certain elements or attributes in them. At this time, if we need to operate on the style sheet links in HTML, we can use regular expressions in PHP to match these links.

The following is an example of how to implement it:

First, we need to get the content of the HTML page and store it in a variable. You can use PHP's file_get_contents function to achieve this operation, for example:

$html = file_get_contents("http://www.example.com");

Next, we need to write the regular Expression to match style sheet links in HTML. Stylesheet links usually have the following format:

Also, there are a few possibilities Variations, such as including absolute or relative paths in the href attribute value, or using the attribute value in double or single quotes, etc. Therefore, we need to write a regular expression that can match various variant stylesheet links.

The following is a regular expression that matches style sheet links:

$link_pattern = '/href=['"]?(..css )/';

This regular expression starts with ) until it encounters the href attribute. Next, we use ['"]? to match The attribute value in quotes or single quotes and stores this value in a group. Finally, we use ..css to match filenames ending in .css in the href attribute value.

After completion, we can use the preg_match_all function to match all style sheet links in the HTML page:

preg_match_all($link_pattern, $html, $matches);

This function will return an array $matches, which contains all matching style sheet links. The element $matches[0] contains all matched strings, while $matches[1] contains the matched href attribute value.

Finally, we can operate on the style sheet links, such as removing or replacing a link:

$new_html = preg_replace($link_pattern, '".

Using regular expressions to match style sheet links in HTML can easily automate page processing. When writing regular expressions, you need to take into account various variations to ensure that all style sheet links are matched.

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