Since version 1.4.9 the public method fpwCategoryThumbnails::addThumbnailToPost is available to plugins developers in both back and front end. There are three ways to add a post thumbnail to a post:

1. manual – assignment of the Featured Image to the post while adding or modifying through admin user interface
2. automatic – while the post is being created or modified – Add New Post or Edit Post admin screens
3. pressing Apply Mapping button of plugin's settings page

However, there are cases when a post is being created / modified outside of the admin user interface. In such cases the assignment of a thumbnail does not occur. The following example shows how to assign or change post thumbnail in one of this cases.

$myPost = array(

    // all neccessary post's elements

);

$post_id = wp_insert_post( $myPost );  // create or modify a post bypassing 'save_post' action

// check if post is ceated / modified and the method exists

if ( $post_id && method_exists( 'fpwCategoryThumbnails', 'addThumbnailToPost' ) ) {

    $post = get_post( $post_id );

    // thumbnail assignment

    fpwCategoryThumbnails::addThumbnailToPost( $post_id, $post );

}