PHP Regular Expression Tutorial: Practical Tips for Removing HTML Tags

PHP regular expression is a powerful tool that can be used to process various patterns and rules in text. In web development, we often encounter the need to remove HTML tags, such as filtering out HTML tags from user input, or extracting plain text from web content. This tutorial will introduce how to use PHP regular expressions to remove HTML tags and give specific code examples.

1. Use regular expressions to remove HTML tags

In PHP, you can use regular expressions to match and replace HTML tags. Here is a simple example that demonstrates how to remove HTML tags from text:

$text = "<h1 id="Hello-strong-World-strong">Hello, <strong>World</strong>!</h1>";
$clean_text = preg_replace("/<.*?>/", "", $text);
echo $clean_text;

In this example, we use the preg_replace function to replace all HTML tags in the text. The regular expression /<.*?>/ matches any HTML tag and replaces it with an empty string, achieving the effect of removing HTML tags.

2. Remove specified tags

Sometimes we may only want to remove specific HTML tags, while retaining other tags and text content. The following example shows how to remove the <script> and <style> tags:

$text = "<h1 id="Hello-script-alert-World-script">Hello, <script> alert('World');</script>!</h1>";
$clean_text = preg_replace("/<script(.*?)</script>|<style(.*?)</style>/is", "", $text);
echo $clean_text;

In this example, we use a specific regular expression/<script(.*?)</script>|<style(.*?)&lt ;/style>/is to match the <script> and <style> tags and their contents, and replace them with the empty string.

3. Extract plain text content

Sometimes we need to extract the plain text content in the HTML document, that is, only keep the text after removing all HTML tags. The following example shows how to extract plain text content:

$html = "<p>This is <strong>bold</strong> and <em>italic</em> text.< /p>";
$clean_text = strip_tags($html);
echo $clean_text;

In this example, we use PHP’s built-in strip_tags function to remove all HTML tags and keep only the text content.

Conclusion

Through this tutorial, you learned how to use PHP regular expressions to remove HTML tags, including removing all tags, removing specific tags, and extracting plain text content. Regular expressions are very useful when dealing with complex patterns and rules in text. I hope you found this tutorial helpful!

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