How to use domain_exists filter in WordPress

So, you’re diving into the world of WordPress hooks, huh? Let’s chat about the domain_exists filter. This hook is pretty neat because it helps you check if a domain or path exists within your network settings. You can use it to ensure you’re not duplicating site names in your multisite installations.

First, you need to register the domain_exists filter. You can do this in your theme’s functions.php file or, better yet, in a custom WordPress plugin. This way, your functionality won’t break if you update your theme.

The domain_exists filter takes four parameters: $result, $domain, $path, and $network_id. Let’s break down what each of these means:

• $result: The site ID if the site name exists, null otherwise.
• $domain: The domain to be checked.
• $path: The path to be checked.
• $network_id: Relevant only on multi-network installations.

Alright, enough talking. Let’s see some real examples!

Example 1: Basic Usage

Here’s how you can use the domain_exists filter to modify the result based on your site’s requirements.

  function weplugins_modify_domain_exists_defaults($result, $domain, $path, $network_id) {
      // Update the $result variable according to your website requirements and return this variable. You can modify the $result variable conditionally too if you want.
      return $result;
  }
  // Add the filter
  add_filter("domain_exists", "weplugins_modify_domain_exists_defaults", 10, 4);
  

Example 2: Conditional Modification

Sometimes, you might want to modify the result conditionally. Here’s how you can do that:

  function weplugins_modify_domain_exists_conditionally($result, $domain, $path, $network_id) {
      if ($domain == 'example.com') {
          $result = null; // Example condition
      }
      return $result;
  }
  // Add the filter
  add_filter("domain_exists", "weplugins_modify_domain_exists_conditionally", 10, 4);
  

Example 3: Removing the Hook

If you need to remove a registered hook, you can use the remove_filter function. Make sure you provide the same callback function name, priority, and the number of arguments.

  // Remove the filter
  remove_filter("domain_exists", "weplugins_modify_domain_exists_defaults", 10, 4);
  

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