WordPress AJAX PHP变量

Question

If I take Wordpresses AJAX/PHP example how would I call $whatever in another function? If I do get a result outside of the initial function (below) it is always 0.

add_action( 'wp_ajax_my_action', 'my_action_callback' );

function my_action_callback() {
    global $wpdb; // this is how you get access to the database

    $whatever = intval( $_POST['whatever'] );

    $whatever += 10;

        echo $whatever; //

    die();
}

Wordpress AJAX plugin code example page

I suspect it is very simple but when you get in a certain mindset you cannot look beyond the blinders.

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