l wpdb $wpdb WordPress database abstraction object.
	 */
	public function update_user_level_from_caps() {
		global $wpdb;
		$this->user_level = array_reduce( array_keys( $this->allcaps ), array( $this, 'level_reduction' ), 0 );
		update_user_meta( $this->ID, $wpdb->get_blog_prefix() . 'user_level', $this->user_level );
	}

	/**
	 * Adds capability and grant or deny access to capability.
	 *
	 * @since 2.0.0
	 *
	 * @param string $cap   Capability name.
	 * @param bool   $grant Whether to grant capability to user.
	 */
	public function add_cap( $cap, $grant = true ) {
		$this->caps[ $cap ] = $grant;
		update_user_meta( $this->ID, $this->cap_key, $this->caps );
		$this->get_role_caps();
		$this->update_user_level_from_caps();
	}

	/**
	 * Removes capability from user.
	 *
	 * @since 2.0.0
	 *
	 * @param string $cap Capability name.
	 */
	public function remove_cap( $cap ) {
		if ( ! isset( $this->caps[ $cap ] ) ) {
			return;
		}
		unset( $this->caps[ $cap ] );
		update_user_meta( $this->ID, $this->cap_key, $this->caps );
		$this->get_role_caps();
		$this->update_user_level_from_caps();
	}

	/**
	 * Removes all of the capabilities of the user.
	 *
	 * @since 2.1.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 */
	public function remove_all_caps() {
		global $wpdb;
		$this->caps = array();
		delete_user_meta( $this->ID, $this->cap_key );
		delete_user_meta( $this->ID, $wpdb->get_blog_prefix() . 'user_level' );
		$this->get_role_caps();
	}

	/**
	 * Returns whether the user has the specified capability.
	 *
	 * This function also accepts an ID of an object to check against if the capability is a meta capability. Meta
	 * capabilities such as `edit_post` and `edit_user` are capabilities used by the `map_meta_cap()` function to
	 * map to primitive capabilities that a user or role has, such as `edit_posts` and `edit_others_posts`.
	 *
	 * Example usage:
	 *
	 *     $user->has_cap( 'edit_posts' );
	 *     $user->has_cap( 'edit_post', $post->ID );
	 *     $user->has_cap( 'edit_post_meta', $post->ID, $meta_key );
	 *
	 * While checking against a role in place of a capability is supported in part, this practice is discouraged as it
	 * may produce unreliable results.
	 *
	 * @since 2.0.0
	 * @since 5.3.0 Formalized the existing and already documented `...$args` parameter
	 *              by adding it to the function signature.
	 *
	 * @see map_meta_cap()
	 *
	 * @param string $cap     Capability name.
	 * @param mixed  ...$args Optional further parameters, typically starting with an object ID.
	 * @return bool Whether the user has the given capability, or, if an object ID is passed, whether the user has
	 *              the given capability for that object.
	 */
	public function has_cap( $cap, ...$args ) {
		if ( is_numeric( $cap ) ) {
			_deprecated_argument( __FUNCTION__, '2.0.0', __( 'Usage of user levels is deprecated. Use capabilities instead.' ) );
			$cap = $this->translate_level_to_cap( $cap );
		}

		$caps = map_meta_cap( $cap, $this->ID, ...$args );

		// Multisite super admin has all caps by definition, Unless specifically denied.
		if ( is_multisite() && is_super_admin( $this->ID ) ) {
			if ( in_array( 'do_not_allow', $caps, true ) ) {
				return false;
			}
			return true;
		}

		// Maintain BC for the argument passed to the "user_has_cap" filter.
		$args = array_merge( array( $cap, $this->ID ), $args );

		/**
		 * Dynamically filter a user's capabilities.
		 *
		 * @since 2.0.0
		 * @since 3.7.0 Added the `$user` parameter.
		 *
		 * @param bool[]   $allcaps Array of key/value pairs where keys represent a capability name
		 *                          and boolean values represent whether the user has that capability.
		 * @param string[] $caps    Required primitive capabilities for the requested capability.
		 * @param array    $args {
		 *     Arguments that accompany the requested capability check.
		 *
		 *     @type string    $0 Requested capability.
		 *     @type int       $1 Concerned user ID.
		 *     @type mixed  ...$2 Optional second and further parameters, typically object ID.
		 * }
		 * @param WP_User  $user    The user object.
		 */
		$capabilities = apply_filters( 'user_has_cap', $this->allcaps, $caps, $args, $this );

		// Everyone is allowed to exist.
		$capabilities['exist'] = true;

		// Nobody is allowed to do things they are not allowed to do.
		unset( $capabilities['do_not_allow'] );

		// Must have ALL requested caps.
		foreach ( (array) $caps as $cap ) {
			if ( empty( $capabilities[ $cap ] ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * Converts numeric level to level capability name.
	 *
	 * Prepends 'level_' to level number.
	 *
	 * @since 2.0.0
	 *
	 * @param int $level Level number, 1 to 10.
	 * @return string
	 */
	public function translate_level_to_cap( $level ) {
		return 'level_' . $level;
	}

	/**
	 * Sets the site to operate on. Defaults to the current site.
	 *
	 * @since 3.0.0
	 * @deprecated 4.9.0 Use WP_User::for_site()
	 *
	 * @param int $blog_id Optional. Site ID, defaults to current site.
	 */
	public function for_blog( $blog_id = '' ) {
		_deprecated_function( __METHOD__, '4.9.0', 'WP_User::for_site()' );

		$this->for_site( $blog_id );
	}

	/**
	 * Sets the site to operate on. Defaults to the current site.
	 *
	 * @since 4.9.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param int $site_id Site ID to initialize user capabilities for. Default is the current site.
	 */
	public function for_site( $site_id = '' ) {
		global $wpdb;

		if ( ! empty( $site_id ) ) {
			$this->site_id = absint( $site_id );
		} else {
			$this->site_id = get_current_blog_id();
		}

		$this->cap_key = $wpdb->get_blog_prefix( $this->site_id ) . 'capabilities';

		$this->caps = $this->get_caps_data();

		$this->get_role_caps();
	}

	/**
	 * Gets the ID of the site for which the user's capabilities are currently initialized.
	 *
	 * @since 4.9.0
	 *
	 * @return int Site ID.
	 */
	public function get_site_id() {
		return $this->site_id;
	}

	/**
	 * Gets the available user capabilities data.
	 *
	 * @since 4.9.0
	 *
	 * @return bool[] List of capabilities keyed by the capability name,
	 *                e.g. `array( 'edit_posts' => true, 'delete_posts' => false )`.
	 */
	private function get_caps_data() {
		$caps = get_user_meta( $this->ID, $this->cap_key, true );

		if ( ! is_array( $caps ) ) {
			return array();
		}

		return $caps;
	}
}