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strip_tags() vs wp_strip_all_tags(): Choosing the Right Tool for Stripping Tags in WordPress

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When developing in WordPress, managing HTML and PHP tags in user inputs and content is essential for both security and proper display. Two popular functions for removing tags are strip_tags() and wp_strip_all_tags(). While both strip out unwanted tags from a string, they cater to different needs and handle HTML and PHP content uniquely. In this article, we’ll compare strip_tags() and wp_strip_all_tags() to help you decide which one is best suited for your WordPress projects.


Understanding strip_tags()

The strip_tags() function is a core PHP function commonly used across various web applications. It removes all HTML and PHP tags from a string, making it easier to work with plain text. However, it lacks WordPress-specific handling, which may make it unsuitable for certain scenarios within WordPress development.

Key Characteristics of strip_tags()
  1. Core PHP Function: Unlike WordPress-specific functions, strip_tags() is a standard PHP function, meaning it’s available in any PHP environment, not just WordPress.
  2. Removes All Tags by Default: By default, strip_tags() removes all HTML and PHP tags within a string, leaving only the plain text. However, it provides flexibility to retain specific tags.
  3. Does Not Handle WordPress Edge Cases: strip_tags() doesn’t specifically address WordPress requirements, such as stripping out content within <script> or <style> tags, which may introduce security or styling issues.
  4. No Special Character Encoding: strip_tags() leaves special HTML entities as they are, meaning some HTML symbols might still be visible or cause encoding issues.
Usage Examples of strip_tags()

Using strip_tags() is straightforward:

$text = '<p>Hello <b>world</b>!</p>';
$clean_text = strip_tags($text); // Output: Hello world!

In this example, strip_tags() removes all tags, including the <p> and <b> tags.

If you want to allow certain tags, pass them as a second parameter:

$clean_text = strip_tags($text, '<b>'); // Output: Hello <b>world</b>!

This retains the <b> tag while removing others. This selective allowance feature is valuable in some scenarios, but it lacks specific handling for tags that may affect security or styling, such as <script> or <style>.


Understanding wp_strip_all_tags()

In contrast to strip_tags(), wp_strip_all_tags() is a WordPress-specific function designed to meet the platform’s requirements for content security and formatting. It provides an extra layer of control by addressing potential WordPress-specific issues.

Key Characteristics of wp_strip_all_tags()
  • WordPress-Specific Function: Created with WordPress in mind, wp_strip_all_tags() handles unique needs related to content safety, making it ideal for WordPress development.
  • Strips All HTML and PHP Tags Without Exception: Unlike strip_tags(), wp_strip_all_tags() does not allow selective tag retention. All tags are stripped, ensuring a consistent plain-text output.
  • Removes Content Inside <script> and <style> Tags: One of the key features of wp_strip_all_tags() is its ability to strip out the content within <script> and <style> tags, reducing the risk of security vulnerabilities or unwanted styles.
  • Encodes Special Characters: wp_strip_all_tags() converts HTML entities to their respective characters, making it safer and cleaner for WordPress usage.
Usage Example of wp_strip_all_tags()

Here’s a basic example of wp_strip_all_tags() in action:

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$text = '<p>Hello <b>world</b>! <script>alert("hi")</script></p>';
$clean_text = wp_strip_all_tags($text); // Output: Hello world!

In this case, wp_strip_all_tags() not only removes the HTML tags but also strips out the content within the <script> tag. This is crucial for enhancing security, particularly when dealing with user-generated content, as it prevents potential JavaScript injections.


Comparing strip_tags() and wp_strip_all_tags()

Now that we understand the individual characteristics of strip_tags() and wp_strip_all_tags(), let’s compare them side-by-side to see how they differ.

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Featurestrip_tags()wp_strip_all_tags()
TypeCore PHP functionWordPress-specific function
Removes All TagsYes, but allows specific tags to remainYes, without exceptions
Removes <script> & <style> ContentNoYes
Encodes Special CharactersNoYes
Use CaseGeneral PHP applications where some tags may be allowedWordPress sites needing comprehensive tag and content removal
Choosing Between strip_tags() and wp_strip_all_tags()
  • Use strip_tags() if you:
  • Need to allow specific tags within a string.
  • Are working in a non-WordPress PHP environment and don’t require advanced tag stripping.
  • Are confident that input sources are safe and don’t include harmful code within <script> or <style> tags.
  • Use wp_strip_all_tags() if you:
  • Are working within WordPress and need comprehensive tag removal.
  • Want to ensure that all HTML and PHP tags are stripped, including potentially harmful script and style content.
  • Require encoded special characters for safer output in a WordPress context.

Real-World Scenarios: Which Function Should You Use?

Understanding when to use each function depends on your project requirements and the nature of the input. Here are some common scenarios in WordPress plugin development where each function might be applied:

  1. User-Generated Content: If you’re handling form inputs, comments, or other user-generated content in WordPress, wp_strip_all_tags() is typically the better choice. It removes all tags comprehensively, including any script or style content that could introduce vulnerabilities.
  2. Displaying Text with Allowed Tags: When you want to display content with specific HTML tags, such as <strong> for bold text or <em> for italics, strip_tags() allows you to selectively retain certain tags. This can be useful for blog posts or descriptions that need minimal formatting.
  3. Sanitizing Titles or Headlines: If you’re sanitizing titles or headlines where tags are unnecessary, wp_strip_all_tags() ensures complete stripping of all tags and unwanted content. It’s especially helpful if you’re pulling content from external sources or user inputs where you can’t control the initial formatting.
  4. Database Storage for Plain Text: When saving text to the database for later display, it’s essential to ensure it’s clean and free from HTML or PHP code. wp_strip_all_tags() is ideal for this purpose, ensuring that all tags are removed without the risk of inadvertently storing harmful scripts.

Summary: Deciding the Best Approach

In WordPress development, security and consistency are essential, especially when dealing with user-generated content. Both strip_tags() and wp_strip_all_tags() play critical roles in different scenarios:

  • strip_tags() is more versatile, allowing you to retain specific tags, but doesn’t account for WordPress-specific security needs, making it better for controlled environments where certain tags need to remain.
  • wp_strip_all_tags() is robust for WordPress-specific projects, offering secure, comprehensive tag stripping that covers script and style content, providing a safe, tag-free output for WordPress websites and plugins.

By choosing the right tool for the job, you can ensure that your WordPress plugins and websites remain both user-friendly and secure. Properly managing tags and content is a small yet powerful step in improving the overall safety and performance of your WordPress projects.

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