I am also having issues with the ‘post_title’ attribute when creating a new post. It isn’t working at all for me, when using all the documentation I see online.
None of these work:
'post_title' => $_POST['fields']['field_53dd8f9f80dad'], // NO
'post_title' => $_POST['acf']['field_53dd8f9f80dad'], // NO
'post_title' => $_POST['field_53dd8f9f80dad'], // NO
'post_title' => $_POST['acf-field_53dd8f9f80dad'], // NO