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PHP Short Tags: Should You Use Them?

By Filip on 11/04/2024

Learn about the pros and cons of using PHP short tags and whether they are a suitable choice for your projects.

PHP Short Tags: Should You Use Them?

Table of Contents

Introduction

PHP, a versatile server-side scripting language, provides flexibility even in how you open and close PHP tags within your code. This article explores the different PHP tag styles, their implications, and why certain styles are preferred over others. We'll delve into standard tags, short tags, and short echo tags, highlighting their advantages and potential drawbacks. Understanding these nuances will empower you to write cleaner, more compatible, and maintainable PHP code.

Step-by-Step Guide

PHP offers different ways to write tags:

  • Standard tags: <?php ?> - Always enabled, recommended for best compatibility.

    <?php echo 'Hello'; ?>

  • Short tags: <? ?> - Can be enabled/disabled in php.ini ( short_open_tag=On ). Not recommended due to potential conflicts and portability issues.

    <? echo 'Hello'; ?>

  • Short echo tags: <?= ?> - Specifically for echoing. Available since PHP 5.4 regardless of short_open_tag setting. Generally considered safe to use.

    <?= 'Hello' ?>

Why are short tags discouraged?

  • Portability: Different servers might have different configurations. Code relying on short tags might break if short_open_tag is off.
  • Conflicts: Short tags can conflict with XML declarations (<?xml version="1.0"?>), especially common in older codebases.

The <?= exception:

While short tags are generally discouraged, the short echo tag <?= ?> is widely accepted. It's concise, readable, and its availability since PHP 5.4 makes it reliable in most modern environments.

In summary:

  • Stick to <?php ?> for maximum compatibility and avoid potential issues.
  • While <?= ?> is generally safe, consider your project's context and coding standards.

Code Example

The code demonstrates different ways to write PHP tags, highlighting the recommended use of standard tags (<?php ?>) over short tags (<? ?>) for better compatibility. It also shows the concise syntax of short echo tags (<?= ?>) and warns about potential conflicts between short tags and XML data, providing a solution using htmlspecialchars().

<?php
// Standard tags - recommended
echo 'Hello with standard tags! <br>'; 

// Short tags - discouraged (might not work depending on server settings)
// <? echo 'Hello with short tags! <br>'; ?> 

// Short echo tags - generally safe and concise
?>
<?= 'Hello with short echo tags! <br>' ?> 

<?php
// Demonstrating potential conflict with XML
$data = '<?xml version="1.0"?><note><to>User</to><from>PHP</from></note>';

// This will break if short tags are enabled
// echo $data; 

// Correct way to handle this:
echo htmlspecialchars($data); 
?>

Explanation:

  1. Standard Tags: The code starts by demonstrating the recommended way of writing PHP tags using <?php ?>. This ensures your code works consistently across different PHP configurations.

  2. Short Tags (Commented Out): The example of short tags <? ?> is commented out. This is intentional to prevent potential errors if your server settings have short_open_tag disabled.

  3. Short Echo Tags: The code then shows the use of short echo tags <?= ?> to directly output the string "Hello with short echo tags!". This syntax is generally considered safe and is widely used for its conciseness.

  4. Conflict with XML: The example demonstrates how short tags can lead to conflicts with XML data. If short tags were enabled, the XML declaration (<?xml version="1.0"?>) would be interpreted as a PHP tag, causing an error. The code shows the correct way to handle this situation using htmlspecialchars() to display the XML content without interpretation.

Key Takeaways:

  • Prioritize using standard tags (<?php ?>) for reliability and compatibility.
  • While tempting for their brevity, avoid short tags (<? ?>) to prevent potential issues.
  • Short echo tags (<?= ?>) offer a good balance of conciseness and safety in most modern PHP environments.
  • Be mindful of potential conflicts with XML data when using short tags.

Additional Notes

  • Configuration: The short_open_tag setting is found in the php.ini file. You might need to restart your web server after making changes to this file for them to take effect.
  • Security Implications: While not a direct security risk, enabling short tags on a server that hosts diverse applications can increase the attack surface if any of those applications have vulnerabilities related to how they handle user input and short tags.
  • Modern PHP: With the widespread adoption of PHP 5.4 and later, the argument against short echo tags (<?= ?>) has significantly weakened. However, consistency within a codebase and adherence to coding standards are still important considerations.
  • Frameworks and CMS: Many popular PHP frameworks and content management systems (like Laravel and WordPress) have their own coding standards that often recommend or enforce the use of standard tags for consistency and best practices.
  • Learning Resources: The official PHP documentation is the best resource for detailed information about PHP tags and configuration options: https://www.php.net/manual/en/language.basic-syntax.phptags.php
  • Alternatives to Short Echo Tags: Even if you decide to avoid <?= ?>, there are other ways to achieve concise output, such as using printf() or template engines like Twig or Blade (in Laravel).
  • Legacy Code: When dealing with legacy PHP code, you might encounter short tags. It's generally a good practice to refactor them to standard tags if possible, especially if you plan to migrate the code to a newer PHP version or a different server environment.

Summary

Tag Type Syntax Availability Recommendation
Standard Tags <?php ?> Always enabled Recommended for best compatibility
Short Tags <? ?> Configurable (short_open_tag in php.ini) Discouraged due to portability and conflict risks
Short Echo Tags <?= ?> PHP 5.4+ (regardless of short_open_tag) Generally safe and widely accepted

Key Takeaways:

  • Standard tags (<?php ?>) are the most reliable and portable choice.
  • Short tags (<? ?>) can cause issues and should be avoided.
  • Short echo tags (<?= ?>) are generally safe to use in modern environments.

Remember: Always prioritize code clarity, compatibility, and adherence to project standards.

Conclusion

In conclusion, while PHP offers various ways to write tags, adhering to the standard <?php ?> tags is crucial for ensuring optimal code compatibility and maintainability. Although short tags may seem appealing due to their brevity, they can introduce portability issues and potential conflicts, making them unsuitable for projects emphasizing robustness. While the short echo tag <?= ?> is generally considered safe and acceptable in modern PHP environments, consistency with project standards and coding conventions should always be prioritized. By understanding the nuances of PHP tags and opting for the most reliable approach, developers can write cleaner, more efficient, and error-free code.

References

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