if ( ! function_exists( 'set_my_featured_image' ) ) {
	add_action( 'save_post', 'set_my_featured_image' );
	function fb_set_featured_image() {
		$postID = get_the_ID();
		if ( has_post_thumbnail( $postID ) ) return NULL;
		if( get_post_type( $postID ) != 'post' ) return NULL;

            $args = array(
                'numberposts'    => 1,
                'order'          => 'DESC', // ASC - pierwsza, DESC -ostatnia
		'orderby'        => 'menu_order', // rand - losowo
                'post_mime_type' => 'image',
                'post_parent'    => $postID,
                'post_status'    => NULL,
                'post_type'      => 'attachment'
            );

            $attached_image = get_children( $args );
            if ( $attached_image ) {
                foreach ( $attached_image as $attachment_id => $attachment )
                    set_post_thumbnail( $postID, $attachment_id );
            }
    }
}