WP_Session mods to recursively check dirty flag

gistfile1.php

	/**
	 * Write the data from the current session to the data storage system.
	 */
	public function write_data() {
		$option_key = "_wp_session_{$this->session_id}";

		// Only write the collection to the DB if it's changed.
		$this->recursive_dirty_check( $this );
		if ( $this->dirty ) {
			if ( false === get_option( $option_key ) ) {
				add_option( "_wp_session_{$this->session_id}", $this->container, '', 'no' );
				add_option( "_wp_session_expires_{$this->session_id}", $this->expires, '', 'no' );
			}
			else {
				delete_option( "_wp_session_{$this->session_id}" );
				add_option( "_wp_session_{$this->session_id}", $this->container, '', 'no' );
			}
		}
	}

	/**
	 * Recursively walk all nodes of this session's container to check dirty status.
	 * Modeled on array_walk_recursive() but visits all nodes, not just leaves
	 *
	 * @param mixed      $node
	 * @param WP_Session $top_node optional - do not specify on the first call
	 *
	 * @return WP_Session
	 */
	private function recursive_dirty_check( $node, WP_Session &$top_node = null ) {

		if ( null === $top_node ) {
			// First call. Set things up and start recursing.
			$top_node = $node;
			return $this->recursive_dirty_check( $node->container, $top_node );
		}
		elseif ( $top_node->dirty ) {
			// Don't recurse further if we already know the data is dirty
			return $top_node;
		}
		elseif ( $node instanceof Recursive_ArrayAccess ) {
			$top_node->dirty = $top_node->dirty || $node->dirty;
			if ( ! $top_node->dirty ) {
				$top_node->dirty = $top_node->dirty || $this->recursive_dirty_check( $node->container, $top_node );
			}
		}
		elseif ( is_array( $node ) ) {
			foreach ( $node as $value ) {
				if ( ! $top_node->dirty ) {
					$top_node->dirty = $top_node->dirty || $this->recursive_dirty_check( $value, $top_node );
				}
			}
		}

		return $top_node;

	}