Site Retrieval Fails In Non-Multisite Environments

[XedinUnknown]

The Symptoms

When activating the plugin, an error message is displayed, saying that the function Dhii\Wp\Containers\get_site() is not found.

Possible Cause

The function get_site() is a WordPress function, but it is not defined in a non-multisite environment. Neither is WP_Site.

Suggested Solution

Even if you require_once() the files with these symbols, i.e. wp-includes/ms-sites.php and wp-includes/class-wp-site.php, get_site() still returns null. Therefore, it is necessary to detect such cases, and perhaps return a fake WP_Site instance if the main site is requested.