How to get the site name during plugin development?

I am developing my first wordpress plugin, and i need to get the site name.

The documentation says to use get_current_site_name( $current_site ) function.

Here is my script

myPlugin.php:

$site_data = get_current_site_name( $current_site );

but get_current_site_name() function is not defined yet.

Also there is no global $current_site variable, as written in documentation.

I also try to add a wp_loaded action, to let the wordpress load fully, but it doesn’t help.

function myfunction() {
     global $current_site;
     $site_data = get_current_site_name( $current_site );
}
add_action('wp_loaded', 'myfunction');

//Fatal error:  Call to undefined function get_current_site_name() in ...

What I’m doing wrong?

Thanks

Update:

There is a bug in this site, when i try to write hello at the top of my question, it strips it automatically. So i’m writing it here – Hello guys 🙂