diff --git a/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php b/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php
index 9844e19460..e773a96734 100644
--- a/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php
+++ b/src/wp-admin/includes/class-bulk-plugin-upgrader-skin.php
@@ -18,6 +18,11 @@
 class Bulk_Plugin_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	public $plugin_info = array(); // Plugin_Upgrader::bulk_upgrade() will fill this in.
 
+	/**
+	 * Function for add strings.
+	 *
+	 * @return void
+	 */
 	public function add_strings() {
 		parent::add_strings();
 		/* translators: 1: Plugin name, 2: Number of the plugin, 3: Total number of plugins being updated. */
@@ -25,6 +30,8 @@ class Bulk_Plugin_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for before title.
+	 *
 	 * @param string $title
 	 */
 	public function before( $title = '' ) {
@@ -32,6 +39,8 @@ class Bulk_Plugin_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for after title.
+	 *
 	 * @param string $title
 	 */
 	public function after( $title = '' ) {
@@ -40,6 +49,7 @@ class Bulk_Plugin_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for perform action of bulk footer.
 	 */
 	public function bulk_footer() {
 		parent::bulk_footer();
diff --git a/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php b/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php
index 94daa27131..7dc8b5091a 100644
--- a/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php
+++ b/src/wp-admin/includes/class-bulk-theme-upgrader-skin.php
@@ -18,6 +18,11 @@
 class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	public $theme_info = array(); // Theme_Upgrader::bulk_upgrade() will fill this in.
 
+	/**
+	 * Function for add strings.
+	 *
+	 * @return void
+	 */
 	public function add_strings() {
 		parent::add_strings();
 		/* translators: 1: Theme name, 2: Number of the theme, 3: Total number of themes being updated. */
@@ -25,6 +30,8 @@ class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for before title.
+	 *
 	 * @param string $title
 	 */
 	public function before( $title = '' ) {
@@ -32,6 +39,8 @@ class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for after title.
+	 *
 	 * @param string $title
 	 */
 	public function after( $title = '' ) {
@@ -40,6 +49,7 @@ class Bulk_Theme_Upgrader_Skin extends Bulk_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for perform action of bulk footer.
 	 */
 	public function bulk_footer() {
 		parent::bulk_footer();
diff --git a/src/wp-admin/includes/class-bulk-upgrader-skin.php b/src/wp-admin/includes/class-bulk-upgrader-skin.php
index 89367c4cf8..250ad48791 100644
--- a/src/wp-admin/includes/class-bulk-upgrader-skin.php
+++ b/src/wp-admin/includes/class-bulk-upgrader-skin.php
@@ -18,11 +18,15 @@
 class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	public $in_loop = false;
 	/**
+	 * Error variable.
+	 *
 	 * @var string|false
 	 */
 	public $error = false;
 
 	/**
+	 * Construct function of class Bulk_Upgrader_Skin
+	 *
 	 * @param array $args
 	 */
 	public function __construct( $args = array() ) {
@@ -36,6 +40,9 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for add strings.
+	 *
+	 * @return void
 	 */
 	public function add_strings() {
 		$this->upgrader->strings['skin_upgrade_start'] = __( 'The update process is starting. This process may take a while on some hosts, so please be patient.' );
@@ -77,12 +84,14 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for header to perform some actions.
 	 */
 	public function header() {
 		// Nothing, This will be displayed within a iframe.
 	}
 
 	/**
+	 * Function for footer to perform some actions.
 	 */
 	public function footer() {
 		// Nothing, This will be displayed within a iframe.
@@ -113,18 +122,26 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for bulk header.
+	 *
+	 * @return void
 	 */
 	public function bulk_header() {
 		$this->feedback( 'skin_upgrade_start' );
 	}
 
 	/**
+	 * Function for bulk footer.
+	 *
+	 * @return void
 	 */
 	public function bulk_footer() {
 		$this->feedback( 'skin_upgrade_end' );
 	}
 
 	/**
+	 * Function for before title.
+	 *
 	 * @param string $title
 	 */
 	public function before( $title = '' ) {
@@ -137,6 +154,8 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for after title.
+	 *
 	 * @param string $title
 	 */
 	public function after( $title = '' ) {
@@ -166,6 +185,7 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for reset data.
 	 */
 	public function reset() {
 		$this->in_loop = false;
@@ -173,6 +193,7 @@ class Bulk_Upgrader_Skin extends WP_Upgrader_Skin {
 	}
 
 	/**
+	 * Function for flush output.
 	 */
 	public function flush_output() {
 		wp_ob_end_flush_all();