I just tested acf_maybe_get_field() on a field that exists but was never saved. The function returns false. I have no idea how you are getting the field key by using that function if the field has no value.
Under these conditions this line should be causing a PHP Undefined Index Warning:
return $maybe_field_obj['key'];
There is no reliable way that I know of using just the field name to get a field key for a field that does not have a value for a specific post.
You could potentially use acf_maybe_get_field() if you supplied a post ID for a post that you know will have the value set. From what I’m hearing there would be no way to know what post ID to use.
You could possibly do a query to get a post where the field key references already exist. Let’s assume that you know that if the field “email” exists for a post and has a field key reference in the db that all other fields will also exist.
$args = array(
'post_type' => 'your-post_type',
'posts_per_page' => 1,
'no_found_rows' => true,
'meta_query' => array(
array(
'key' => '_email'
'compare' => 'EXISTS'
}
)
);
$test_query = new WP_Query($args);
if (!empty($test_query->posts) {
$valid_fields_post_id = $test_query->posts[0]->ID;
}
But this will not work unless you can be sure all of the field references exist. You could also check for the existence of all field key references but I think if you have too many fields you need to check that the query could time out.
