What is the proper way to get logged in user id in a plugin?

Question

I need to get logged in user id inside my plugin.

Is this the proper way?

$root = dirname(dirname(dirname(dirname(__FILE__))));
if (file_exists($root.'/wp-load.php')) {
require_once($root.'/wp-load.php');
} 
$user_id = get_current_user_id();

Otto saying that we shouldn't load wp-load.php file since we have no idea where wp-load.php file located and it doubles the server load.

So I'm really confused.

And one more question..

Check this Rarst's Image

According to that image wp-load.php loaded before all the plugins. So why all plugin authors include that file again?

Answer 1

If you're inside a plugin, WordPress is already loaded. You don't need to load it yourself.

Inside whatever function needs the user ID, you need to do two things:

1. Globalize the user data variable
2. Populate the user data variable

Here's some pseudocode:

function some_function_that_needs_user_info() {
    global $current_user;
    get_currentuserinfo();

    // Now reference $current_user->ID in your code.
}

Answer 2

Use is_user_logged_in() and get_currentuserinfo().

if ( is_user_logged_in() ) {
    // Current user is logged in,
    // so let's get current user info
    global $current_user;
    get_currentuserinfo();
    // User ID
    $user_id = $current_user->ID;
}