Yes, and the function to use depends on the version of Drupal that you're using with your website.

Drupal 6 and 7¶

The function to use is called user_is_logged_in, and it can determine if a given user is logged in. For complete documentation on the function, click the appropriate link from the following, based on your Drupal version:

• Drupal 7 user_is_logged_in function information from drupal.org
• Drupal 6 user_is_logged_in function information from drupal.org

The function is a boolean that returns TRUE if the user is logged in, and FALSE if the user is anonymous.

Note

Functions and their usage can change between Drupal versions.

Drupal 8¶

There are a couple of methods that you can use in Drupal 8 to make this check:

• Use the isAuthenticated() method on the user. For example, use the following code to determine the state of the current user:
  copy

  $logged_in = \Drupal::currentUser()->isAuthenticated();

• Use isAnonymous() to determine if the user is anonymous:
  copy

  \Drupal::currentUser()->isAnonymous();