Why is Wordpress get_the_ID() returning empty?

Question

My code is simple:

$group_id = get_the_ID();
if ( get_post_meta ($group_id, '_um_groups_shells', true) == 'true'){
    wp_set_object_terms( $group_id, array( 'full-shells' ), 'um_group_categories', true );
} elseif ( get_post_meta ($group_id, '_um_groups_shells', true) == 'false'){
    wp_remove_object_terms( $group_id, array( 'full-shells' ), 'um_group_categories', true );
}

I have checked that the conditionals are working correctly by using die("Group:". $group_id);

What I discovered is that in the example die("Group:". $group_id); the $group_id returns 51478 . But if I use just die($group_id); then it is empty.

Based on that, I'm assuming that

wp_set_object_terms( $group_id, array( 'full-shells' ), 'um_group_categories', true );

doesn't work because $group_id must be empty.

If I run it like this:

$group_id = 51478;
wp_set_object_terms( $group_id, array( 'full-shells' ), 'um_group_categories', true );

then it works fine.

Update I tried wpdevloper_j's suggestion of using global $post; $post->ID; global $post; $post->ID; instead. But the same problem occurred. I can echo $group_id and print_r($group_id) and get the correct id, but when trying to execute with wp_set_object_terms it seems to be empty.

What is causing $group_id to be empty?

When I do var_dump ($group_id) , I receive int(51478)

Updated Solution The problem was with a subsequent line of code:

wp_set_object_terms( $group_id, $formdata[ 'categories' ], 'um_group_categories', false );

The false parameter was undoing the previous. So it was executing and then updating again after the successful execution.

That was so frustrating. :(

Answer 1

die() — Equivalent to exit

exit ( string $status = ? ) : void
exit ( int $status ) : void

https://www.php.net/manual/en/function.exit.php