istered' ), true ) ) {
			$_orderby = 'user_' . $orderby;
		} elseif ( in_array( $orderby, array( 'user_login', 'user_nicename', 'user_email', 'user_url', 'user_registered' ), true ) ) {
			$_orderby = $orderby;
		} elseif ( 'name' === $orderby || 'display_name' === $orderby ) {
			$_orderby = 'display_name';
		} elseif ( 'post_count' === $orderby ) {
			// @todo Avoid the JOIN.
			$where             = get_posts_by_author_sql( 'post' );
			$this->query_from .= " LEFT OUTER JOIN (
				SELECT post_author, COUNT(*) as post_count
				FROM $wpdb->posts
				$where
				GROUP BY post_author
			) p ON ({$wpdb->users}.ID = p.post_author)";
			$_orderby          = 'post_count';
		} elseif ( 'ID' === $orderby || 'id' === $orderby ) {
			$_orderby = 'ID';
		} elseif ( 'meta_value' === $orderby || $this->get( 'meta_key' ) === $orderby ) {
			$_orderby = "$wpdb->usermeta.meta_value";
		} elseif ( 'meta_value_num' === $orderby ) {
			$_orderby = "$wpdb->usermeta.meta_value+0";
		} elseif ( 'include' === $orderby && ! empty( $this->query_vars['include'] ) ) {
			$include     = wp_parse_id_list( $this->query_vars['include'] );
			$include_sql = implode( ',', $include );
			$_orderby    = "FIELD( $wpdb->users.ID, $include_sql )";
		} elseif ( 'nicename__in' === $orderby ) {
			$sanitized_nicename__in = array_map( 'esc_sql', $this->query_vars['nicename__in'] );
			$nicename__in           = implode( "','", $sanitized_nicename__in );
			$_orderby               = "FIELD( user_nicename, '$nicename__in' )";
		} elseif ( 'login__in' === $orderby ) {
			$sanitized_login__in = array_map( 'esc_sql', $this->query_vars['login__in'] );
			$login__in           = implode( "','", $sanitized_login__in );
			$_orderby            = "FIELD( user_login, '$login__in' )";
		} elseif ( isset( $meta_query_clauses[ $orderby ] ) ) {
			$meta_clause = $meta_query_clauses[ $orderby ];
			$_orderby    = sprintf( 'CAST(%s.meta_value AS %s)', esc_sql( $meta_clause['alias'] ), esc_sql( $meta_clause['cast'] ) );
		}

		return $_orderby;
	}

	/**
	 * Generate cache key.
	 *
	 * @since 6.3.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param array  $args Query arguments.
	 * @param string $sql  SQL statement.
	 * @return string Cache key.
	 */
	protected function generate_cache_key( array $args, $sql ) {
		global $wpdb;

		// Replace wpdb placeholder in the SQL statement used by the cache key.
		$sql = $wpdb->remove_placeholder_escape( $sql );

		$key          = md5( $sql );
		$last_changed = wp_cache_get_last_changed( 'users' );

		if ( empty( $args['orderby'] ) ) {
			// Default order is by 'user_login'.
			$ordersby = array( 'user_login' => '' );
		} elseif ( is_array( $args['orderby'] ) ) {
			$ordersby = $args['orderby'];
		} else {
			// 'orderby' values may be a comma- or space-separated list.
			$ordersby = preg_split( '/[,\s]+/', $args['orderby'] );
		}

		$blog_id = 0;
		if ( isset( $args['blog_id'] ) ) {
			$blog_id = absint( $args['blog_id'] );
		}

		if ( $args['has_published_posts'] || in_array( 'post_count', $ordersby, true ) ) {
			$switch = $blog_id && get_current_blog_id() !== $blog_id;
			if ( $switch ) {
				switch_to_blog( $blog_id );
			}

			$last_changed .= wp_cache_get_last_changed( 'posts' );

			if ( $switch ) {
				restore_current_blog();
			}
		}

		return "get_users:$key:$last_changed";
	}

	/**
	 * Parses an 'order' query variable and casts it to ASC or DESC as necessary.
	 *
	 * @since 4.2.0
	 *
	 * @param string $order The 'order' query variable.
	 * @return string The sanitized 'order' query variable.
	 */
	protected function parse_order( $order ) {
		if ( ! is_string( $order ) || empty( $order ) ) {
			return 'DESC';
		}

		if ( 'ASC' === strtoupper( $order ) ) {
			return 'ASC';
		} else {
			return 'DESC';
		}
	}

	/**
	 * Makes private properties readable for backward compatibility.
	 *
	 * @since 4.0.0
	 * @since 6.4.0 Getting a dynamic property is deprecated.
	 *
	 * @param string $name Property to get.
	 * @return mixed Property.
	 */
	public function __get( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return $this->$name;
		}

		wp_trigger_error(
			__METHOD__,
			"The property `{$name}` is not declared. Getting a dynamic property is " .
			'deprecated since version 6.4.0! Instead, declare the property on the class.',
			E_USER_DEPRECATED
		);
		return null;
	}

	/**
	 * Makes private properties settable for backward compatibility.
	 *
	 * @since 4.0.0
	 * @since 6.4.0 Setting a dynamic property is deprecated.
	 *
	 * @param string $name  Property to check if set.
	 * @param mixed  $value Property value.
	 */
	public function __set( $name, $value ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			$this->$name = $value;
			return;
		}

		wp_trigger_error(
			__METHOD__,
			"The property `{$name}` is not declared. Setting a dynamic property is " .
			'deprecated since version 6.4.0! Instead, declare the property on the class.',
			E_USER_DEPRECATED
		);
	}

	/**
	 * Makes private properties checkable for backward compatibility.
	 *
	 * @since 4.0.0
	 * @since 6.4.0 Checking a dynamic property is deprecated.
	 *
	 * @param string $name Property to check if set.
	 * @return bool Whether the property is set.
	 */
	public function __isset( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			return isset( $this->$name );
		}

		wp_trigger_error(
			__METHOD__,
			"The property `{$name}` is not declared. Checking `isset()` on a dynamic property " .
			'is deprecated since version 6.4.0! Instead, declare the property on the class.',
			E_USER_DEPRECATED
		);
		return false;
	}

	/**
	 * Makes private properties un-settable for backward compatibility.
	 *
	 * @since 4.0.0
	 * @since 6.4.0 Unsetting a dynamic property is deprecated.
	 *
	 * @param string $name Property to unset.
	 */
	public function __unset( $name ) {
		if ( in_array( $name, $this->compat_fields, true ) ) {
			unset( $this->$name );
			return;
		}

		wp_trigger_error(
			__METHOD__,
			"A property `{$name}` is not declared. Unsetting a dynamic property is " .
			'deprecated since version 6.4.0! Instead, declare the property on the class.',
			E_USER_DEPRECATED
		);
	}

	/**
	 * Makes private/protected methods readable for backward compatibility.
	 *
	 * @since 4.0.0
	 *
	 * @param string $name      Method to call.
	 * @param array  $arguments Arguments to pass when calling.
	 * @return mixed Return value of the callback, false otherwise.
	 */
	public function __call( $name, $arguments ) {
		if ( 'get_search_sql' === $name ) {
			return $this->get_search_sql( ...$arguments );
		}
		return false;
	}
}