Tự động set ảnh đầu tiên là featured image cho module auto-upload-images

$success = (bool) $wpdb->update($wpdb->posts, array('post_content' => $content), array('ID' => $post->ID));
        $thumb_id = 0;
        $thumb_id = $this->get_first_content_image_id( $content );
        if ($thumb_id > 0)
            update_post_meta( $post->ID, '_thumbnail_id', $thumb_id );
 
        return $success;

private function get_first_content_image_id ( $content ) {
        // set variables
        global $wpdb;
        // look for images in HTML code
        preg_match_all( '/<[iI][mM][gG][^>]+>/', $content, $all_img_tags );
        if ( $all_img_tags ) {
            foreach ( $all_img_tags[ 0 ] as $img_tag ) {
                // find class attribute and catch its value
                preg_match( '/<img[^>]*class\s*=\s*[\'"]([^\'"]+)[\'"][^>]*>/i', $img_tag, $img_class );
                if ( $img_class ) {
                    // Look for the WP image id
                    preg_match( '/wp-image-([\d]+)/i', $img_class[ 1 ], $found_id );
                    // if first image id found: check whether is image
                    if ( $found_id ) {
                        $img_id = absint( $found_id[ 1 ] );
                        // if is image: return its id
                        if ( wp_attachment_is_image( $img_id ) ) {
                            return $img_id;
                        }
                    } // if(found_id)
                } // if(img_class)
 
                // else: try to catch content image id by its url as stored in the database
                // find src attribute and catch its value
                preg_match( '/<img[^>]*src\s*=\s*[\'"]([^\'"]+)[\'"][^>]*>/i', $img_tag, $img_src );
                if ( $img_src ) {
                    // delete optional query string in img src
                    $url = preg_replace( '/([^?]+).*/', '\1', $img_src[ 1 ] );
                    // delete image dimensions data in img file name, just take base name and extension
                    $guid = preg_replace( '/(.+)-\d+x\d+\.(\w+)/', '\1.\2', $url );
                    // if path is set relatively make it absolute
                    if ( 0 === strpos( $guid, '/' ) ) {
                        $guid = home_url() . $guid;
                    }
                    // look up its ID in the db
                    $found_id = $wpdb->get_var( $wpdb->prepare( "SELECT `ID` FROM $wpdb->posts WHERE `guid` = '%s'", $guid ) );
                    // if first image id found: return it
                    if ( $found_id ) {
                        return absint( $found_id );
                    } // if(found_id)
 
                } // if(img_src)
            } // foreach(img_tag)
        } // if(all_img_tags)
 
        // if nothing found: return 0
        return 0;
    }