Add Featured Image Data Syndication

This will allow plugin to syndicate such fields as caption, alternative
text and description. It pulls post data and alt-text meat for the
syndicated image and then updates the remote post once image is
successfully uploaded and the attachment ID is created.
It would be easier to do it on the upload stage but xmlrpc media object
is not supporting caption and description fields at the moment.

includes/class-syndication-wp-xmlrpc-client.php

@@ -40,6 +40,7 @@ class Syndication_WP_XMLRPC_Client extends WP_HTTP_IXR_Client implements Syndica
 	}
 
 	function post_push_send_thumbnail( $remote_post_id, $post_id ) {
+
 		$thumbnail_meta_keys = $this->get_thumbnail_meta_keys( $post_id ); 
 
 		foreach ( $thumbnail_meta_keys as $thumbnail_meta ) {
@@ -74,7 +75,11 @@ class Syndication_WP_XMLRPC_Client extends WP_HTTP_IXR_Client implements Syndica
 				continue;
 
 			list( $thumbnail_url ) = wp_get_attachment_image_src( $thumbnail_id, 'full' );
-
+			//pass thumbnail data and meta into the addThumnail to sync caption, description and alt-text
+			//has to be this way since 
+			$thumbnail_post_data = get_post($thumbnail_id);
+			$thumbnail_alt_text = trim(strip_tags(get_post_meta($thumbnail_id, '_wp_attachment_image_alt', true)));
+			
 			$result = $this->query(
 				'syndication.addThumbnail',
 				'1',
@@ -82,7 +87,9 @@ class Syndication_WP_XMLRPC_Client extends WP_HTTP_IXR_Client implements Syndica
 				$this->password,
 				$remote_post_id,
 				$thumbnail_url,
-				$thumbnail_meta
+				$thumbnail_meta,
+				$thumbnail_post_data,
+				$thumbnail_alt_text
 			);
 
 			if ( $result ) {
@@ -415,6 +422,7 @@ class Syndication_WP_XMLRPC_Client_Extensions {
 
 	public static function push_syndicate_methods( $methods ) {
         $methods['syndication.addThumbnail']    = array( __CLASS__, 'xmlrpc_add_thumbnail' );
+        $methods['syndication.addThumbnailData']    = array( __CLASS__, 'xmlrpc_add_thumbnail_data' );
         $methods['syndication.deleteThumbnail']    = array( __CLASS__, 'xmlrpc_delete_thumbnail' );
 		return $methods;
 	}
@@ -430,6 +438,8 @@ class Syndication_WP_XMLRPC_Client_Extensions {
 		$post_ID            = (int)$args[3];
 		$thumbnail_url     = esc_url_raw( $args[4] );
 		$meta_key = ! empty( $args[5] ) ? sanitize_text_field( $args[5] ) : '_thumbnail_id';
+		$thumbnail_post_data = $args[6];
+		$thumbnail_alt_text = $args[7];
 
 		if ( ! $post_ID )
 			return new IXR_Error( 500, __( 'Please specify a valid post_ID.', 'syndication' ) );
@@ -470,6 +480,26 @@ class Syndication_WP_XMLRPC_Client_Extensions {
 
 		if ( ! $thumbnail_set )
 			return new IXR_Error( 403, __( 'Could not attach post thumbnail.' ) );
+		
+		$args = array(
+			$blog_id,
+			$username,
+			$password,
+			$thumbnail_id,
+			array(
+				'post_title' => $thumbnail_post_data['post_title'],
+				'post_content' => $thumbnail_post_data['post_content'],
+				'post_excerpt' => $thumbnail_post_data['post_excerpt'],
+			),
+		);
+		//update caption and description of the image
+		$result = $wp_xmlrpc_server->wp_editPost($args);
+		if ($result !== true) {
+			//failed to update atatchment post details
+			//handle it th way you want it (log it, message it)
+		}
+		//update alt text of the image
+		update_post_meta($thumbnail_id, '_wp_attachment_image_alt', $thumbnail_alt_text);
 
 		return $thumbnail_id;
 	}