Gravity Forms Checkbox Save to Taxonomies

// Add this into your functions.php file for the form.
// This part populates the form with the data already in the database.
// You should edit everything that is IN_ALL_CAPS.
$YOUR_TERMS_VAR = get_the_terms( $post->ID, 'YOUR_TAXONOMY' );
if ( $YOUR_TERMS_VAR && ! is_wp_error( $YOUR_TERMS_VAR ) ) :
    $SELECTED_ITEMS = array();
    foreach ( $YOUR_TERMS_VAR as $term ) {
        //use "slug" instead of "id" or "value"
        $SELECTED_ITEMS[] = $term->slug;
    }
    $teachers = join( ", ", $SELECTED_ITEMS );
endif;
$current_student_data['SELECTED_ITEMS'] = $teachers;


// you may also use "gform_after_submission_##" for a specific form.
add_action( 'gform_after_submission', 'gf_edit_student', 10, 2 );
function gf_edit_student( $entry, $form ) {
    global $post;
    global $wpdb;
    global $wp_query;
    $postID = $wp_query->post->ID;


// YOUR_TERMS_VAR should match what is above.
// This part saves the new data to the database.
// the "." [dot] after the 30 (which should be your ID of your checkbox field) stays.
        $YOUR_TERMS_VAR = array();
        foreach($entry as $field=>$slug){
            if (substr($field, 0, 3) == '30.' ) { //30. = the id of your checkboxes
                $YOUR_TERMS_VAR[] = $slug;
            }
        }


// YOUR_TERMS_VAR should match what is above.
// Edit "YOUR_TAXONOMY" to be your taxonomy name.
wp_set_object_terms($postID, $YOUR_TERMS_VAR, 'YOUR_TAXONOMY');