+ /**
+ * The error/notification strings used to update the user on the progress.
+ *
+ * @since 2.8.0
+ * @var string $strings
+ */
+ public $strings = array();
+
+ /**
+ * The upgrader skin being used.
+ *
+ * @since 2.8.0
+ * @var WP_Upgrader_Skin $skin
+ */
+ public $skin = null;
+
+ /**
+ * The result of the installation.
+ *
+ * This is set by {@see WP_Upgrader::install_package()}, only when the package is installed
+ * successfully. It will then be an array, unless a {@see WP_Error} is returned by the
+ * {@see 'upgrader_post_install'} filter. In that case, the `WP_Error` will be assigned to
+ * it.
+ *
+ * @since 2.8.0
+ * @var WP_Error|array $result {
+ * @type string $source The full path to the source the files were installed from.
+ * @type string $source_files List of all the files in the source directory.
+ * @type string $destination The full path to the install destination folder.
+ * @type string $destination_name The name of the destination folder, or empty if `$destination`
+ * and `$local_destination` are the same.
+ * @type string $local_destination The full local path to the destination folder. This is usually
+ * the same as `$destination`.
+ * @type string $remote_destination The full remote path to the destination folder
+ * (i.e., from `$wp_filesystem`).
+ * @type bool $clear_destination Whether the destination folder was cleared.
+ * }
+ */
+ public $result = array();
+
+ /**
+ * The total number of updates being performed.
+ *
+ * Set by the bulk update methods.
+ *
+ * @since 3.0.0
+ * @var int $update_count
+ */
+ public $update_count = 0;
+
+ /**
+ * The current update if multiple updates are being performed.
+ *
+ * Used by the bulk update methods, and incremented for each update.
+ *
+ * @since 3.0.0
+ * @var int
+ */
+ public $update_current = 0;
+
+ /**
+ * Construct the upgrader with a skin.
+ *
+ * @since 2.8.0
+ *
+ * @param WP_Upgrader_Skin $skin The upgrader skin to use. Default is a {@see WP_Upgrader_Skin}
+ * instance.
+ */
+ public function __construct( $skin = null ) {