Get variable value outside action hook

I'm trying to get current screen within wp-admin for some conditional functions to run based on screeen name as follow :

global $this_screen;
function wporg_current_screen_example( $current_screen ) {
    $this_screen = $current_screen->post_type;
    echo $this_screen; // Returns current screen name
}
add_action( 'current_screen', 'wporg_current_screen_example' );
echo $this_screen; // Always returns empty

Inside function, I do get value for echo $this_screen;

But when I try to get value of echo $this_screen; outside action/function it returns empty.

So, How do I get variable value outside of action hook ?