Hi James,
thanks for your advice. I tried to get the post ID but somehow it didn´t work.
Now my code looks like this:
// Add acf field to product generator page
add_filter('vpc_container_end', 'add_table', 10, 1);
function add_table($value){
global $post;
$value .= get_field('testfield', $post->ID);
return $value;
}
For testing I also tried to enter the ID of a specific post:
$value .= get_field('testfield', 17890);
But this doesn´t work either. :-/