How to show parent pages on a specific page if user is logged in?

Question

I have tried with the code bellow, but it's not working. 43 is the ID of the forum page. Also I'm trying to use is_user_logged_in():

function forumpage()
{
global $post;
global $wp_query;

if ($post->post_parent != 43)
{
    $thePostID = $post->post_parent;
    // echo 'You are not on the forum page';
}
else
{
    $thePostID = $wp_query->post->ID;
    // echo 'You are at the forum page';
}
}
add_action( 'init' , 'forumpage' );

Answer 1

The database hasn't been queried yet on init, there is no $post or $wp_query. See the Action Reference for the order actions are executed. Try moving your code to the template_redirect action.