Can't Output get_post_meta?

Question

I have a custom field for my post and I am trying to output it onto my post's page but nothing appears. I know my code works otherwise if instead of trying to call my custom field, I use a fixed string.

My custom field key has an id of

_dad_wysiwyg

I am using this to try to display the value of the key from within functions.php:

add_action( '__after_content' , 'add_dad_cents' );
function add_dad_cents() {
    echo get_post_meta($post->ID, '_dad_wysiwyg', true);
}

I know the key has a value by looking at my postmeta table in my database. The value of the key is

<p>test</p>

Logically, after my post content, I'd expect to see the above string but nothing appears. As I stated, if I change my function to echo a string, I see the string where expected after my post content.

edit: It appears $post is empty. Clearly, I need help calling the post ID from functions.php...

Can anyone help me figure out how to call the value?

Thanks!

Answer 1

Problem solved.

Added the following to my function:

global $post;