What exactly is it that works, and what doesn't?
I can see one obvious problem with your final code sample, namely mixing up the $post_id, as well as adding post meta to a post that has not been inserted yet.
First, let's clear something up about the filter arguments.
In your example we have two arguments, $post_id, and $form_data.
Now these variable names could be anything, we just need to be consistent when using them throughout the rest of the code.
For post forms the first argument is the id of the newly created post.
For user forms the first argument is actually the id of the newly registered user. The code works if we call it $post_id (we could equally call it $banana), but as it is really the user ID let's use $user_id instead.
Because when you insert a new instructor post, you will need the id of that post to be able to add post meta to it (which you are currently doing in the wrong order).
So, the updated code looks like this:
add_action('cred_save_data', 'my_save_data_action', 10, 2);
function my_save_data_action($user_id, $form_data)
{
global $_POST;
// for testing, delete when done
error_log('_POST: ' . print_r($_POST, true));
if ($form_data['id'] == 11) {
$my_post = array(
'post_title' => $_POST['user_login'],
'post_status' => 'publish',
'post_author' => $user_id,
'post_type' => 'instructor',
);
// Insert the post into the database
$post_id = wp_insert_post($my_post);
if (isset($_POST['wpcf-salutation'])) {
// 'wpcf_salutation-i' is the meta key that the value of 'wpcf_salutation' will be added to
add_post_meta($post_id, 'wpcf_salutation-i', $_POST['wpcf_salutation'], true);
}
if (isset($_POST['wpcf-first-name'])) {
// 'wpcf_first-name-i' is the meta key that the value of 'wpcf_first-name' will be added to
add_post_meta($post_id, 'wpcf_first-name-i', $_POST['wpcf_first-name'], true);
}
}
}
Note that I've included a line for debugging which you can later delete when everything works as expected.
It simply sends the global $_POST object to the debug log so that you can inspect it and make sure it contains everything you need/expect and the format. (You could find the value of the fields such as wpcf-salutation are buried inside an array, for example.)
If you haven't already, turn on the debug log by editing your wp-config.php file and change the line with WP_DEBUG like so:
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);
define('WP_DISABLE_FATAL_ERROR_HANDLER',true);
That will create a debug.log file in your /wp-content/ directory which you can examine in any text editor.
