Comprehending the WordPress Alert: Unable to Include sunrise.php

If you’ve come across the following error while managing a WordPress Multisite setup, you’re in good company:

Warning: include_once(/home/u801461719/domains/scienceblog.com/public_html/wp-content/sunrise.php): 
Failed to open stream: No such file or directory in 
/home/u801461719/domains/scienceblog.com/public_html/wp-includes/ms-settings.php on line 47

Warning: include_once(): Failed opening '/home/u801461719/domains/scienceblog.com/public_html/wp-content/sunrise.php' for inclusion 
(include_path='.:/opt/alt/php82/usr/share/pear:/opt/alt/php82/usr/share/php:/usr/share/pear:/usr/share/php') 
in /home/u801461719/domains/scienceblog.com/public_html/wp-includes/ms-settings.php on line 47

This notification typically arises in WordPress Multisite configurations and may lead to confusion or disrupt website functionality. In this article, we will clarify the meaning of this warning, its causes, and effective ways to address it.

What Is sunrise.php in WordPress?

The sunrise.php file is an optional configuration file for WordPress, principally utilized in Multisite networks with custom domain mapping or enhanced multisite functionalities. When set up, it runs before WordPress fully loads, making it suitable for plugins or custom scripts that need to ascertain which site is being accessed prior to further processing.

This file is generally located in:

/wp-content/sunrise.php

It must also be explicitly declared in your wp-config.php file with the following directive:

define('SUNRISE', 'on');

If this is declared but the sunrise.php file is missing, WordPress generates the warnings you are encountering.

What Do These Warnings Indicate?

Let’s dissect the crucial elements of the warning message:

• include_once(): Failed to open stream: PHP is attempting to include the file sunrise.php, but it cannot find it in the specified path.
• Failed opening for inclusion: PHP tried to include the file but was unable to do so, likely because the file is missing or inaccessible.
• File path: The specific path it’s trying to access is /home/u801461719/domains/scienceblog.com/public_html/wp-content/sunrise.php.

These warnings imply that:

1. The file wp-content/sunrise.php might not exist
2. …or there may be a permissions issue that prevents WordPress from accessing it.

What Causes This Warning?

Common explanations include:

• File Not Found: The sunrise.php file has been deleted, relocated, or was never originally added.
• Misconfiguration: The SUNRISE constant is set to ‘on’ in wp-config.php, while the associated file is absent.
• Problematic Plugin: Certain plugins, particularly those for domain mapping, may require sunrise.php but fail to install it properly.

How to Resolve the Error

Depending on your situation, there are several approaches to rectify the problem:

1. Verify the Necessity of sunrise.php

If you’re not utilizing domain mapping or any specific Multisite functionality, you may not require the sunrise.php file at all. In that case, either remove or comment out the following line from your wp-config.php:

// define('SUNRISE', 'on');

2. Restore or Substitute the File

If you do require sunrise.php, consider restoring it. Here are possible solutions:

• Search for Backups: If you have a backup of your site, try to recover the missing sunrise.php file.
• Reinstall Domain Mapping Plugin: If the absent file was created by a plugin like WordPress MU Domain Mapping, attempt to reinstall or update that plugin. Frequently, the