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How to Log Errors and Debug Information in WordPress Using PHP

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Short introduction

Debugging is an essential part of developing and maintaining a WordPress site. PHP errors and issues can disrupt site functionality, making it crucial to monitor and log these problems effectively. In this guide, we’ll explore how to log errors and debug information in WordPress using PHP.

Why Error Logging and Debugging Are Crucial in WordPress

When running a WordPress site, you may encounter issues such as broken functionality, slow performance, or unexpected behaviors. Error logging and debugging allow developers to:

• Identify issues before they escalate.
• Understand the root cause of errors.
• Optimize code performance and security.
• Provide a better user experience.

Setting Up Error Logging in WordPress

Enable WordPress Debugging

WordPress includes a built-in debugging system controlled through the wp-config.php file. IMPORTANT: Insert the following constants before the /* That's all, stop editing! Happy publishing. */part. To enable debugging, follow these steps:

// Open wp-config.php
define('WP_DEBUG', true);

When "WP_DEBUG" is set to "true", WordPress will display PHP errors and warnings on the frontend. However, exposing error details publicly is not ideal for live websites.

Log Errors Instead of Displaying Them

To log errors into a file instead of showing them to users, configure the following constants:

// Enable logging
define('WP_DEBUG_LOG', true);

// Disable error display on the frontend
define('WP_DEBUG_DISPLAY', false);
@ini_set('display_errors', 0);

The WP_DEBUG_LOG constant creates a debug.log file in the wp-content directory where all errors and warnings will be logged.

Customizing the Log File Location

If you want to store the debug log in a different directory for better organization, use the error_log directive:

// Redirect error log to a custom location
@ini_set('log_errors', 1);
@ini_set('error_log', '/path-to-your-log-folder/debug.log');

Ensure that the specified directory has the proper write permissions.

Using PHP to Manually Log Debug Information

In addition to automated error logging, you can log custom messages or data for debugging purposes using PHP’s error_log function:

// Log a custom error message
error_log('This is a test log message.');

// Log variable data
$data = array('status' => 'success', 'message' => 'Data saved.');
error_log(print_r($data, true));

Best Practices for Custom Logging

• Log only what’s necessary to avoid cluttering the log file.
• Use meaningful messages to describe issues.
• Remove or disable custom logging in production environments.

Advanced Debugging Tools

Using the Query Monitor Plugin

The Query Monitor plugin is a powerful tool for debugging WordPress. It provides insights into database queries, hooks, errors, and PHP warnings directly within the WordPress admin area.

Enabling Xdebug for In-Depth PHP Debugging

Xdebug is an advanced tool for step-by-step PHP debugging. To use it with WordPress:

1. Install Xdebug on your server or local environment.
2. Configure your IDE (e.g., VSCode, PhpStorm) to connect to Xdebug.
3. Set breakpoints in your WordPress code to analyze execution flow.

Troubleshooting Common Issues

Debug Log File Not Created

If the debug.log file is not being created, ensure the wp-content directory is writable and that debugging constants are set correctly in wp-config.php.

Log File Size Growing Too Large

To prevent excessive log file size:

• Rotate log files periodically using a script or server configuration.
• Disable debugging in production environments unless necessary.

Conclusion

By following this guide, you can effectively log errors and debug information in WordPress using PHP. This practice helps you identify and resolve issues, optimize site performance, and maintain a seamless user experience. For more advanced debugging, consider tools like Query Monitor or Xdebug. Happy debugging!