Why does 'get_the_ID' work outside of the loop?

Question

on WordPress Developer Resources website's page related to get_the_ID() function it says:

Retrieves the ID of the current item in the WordPress Loop

But I can use it outside of the loop and it works without using get_queried_object_id() which is apparently recommended in such a case.

Why is that?

(little code snippet to let you understand what I mean):

get_header();

echo get_the_ID(); // Shows the id of currently displayed page.

// Here comes the loop!
$some_query_args...
$some_query_loop {
    echo get_the_ID(); // Shows the id of queried page/post.
}

get_footer();

Answer 1

The get_the_ID() function uses the global $post variable, which outside of the loop is sometimes equal to get_queried_object_id(). Within the loop, the $post variable is set to the current post within the loop.

As to why get_queried_object_id() is recommended outside of the loop, is because it does not use the global $post variable, so is less likely to be corrupted by loops.