A local Valet driver for proxying images to a remote host

LocalValetDriver.php

<?php

/**
 * Class LocalValetDriver
 *
 * This class demonstrates how we might go about proxying any missing local images to a remote host. i.e; the production
 * site. This has been created with WordPress in mind but could be adjusted to work with any other system.
 */
class LocalValetDriver extends WordPressValetDriver {

	/** @var string The remote host to proxy requests to */
	const REMOTE_HOST = 'https://remotehost.com/';

	/** @var string If the request URI starts with this, we want to proxy the request to the remote host */
	const URI_PREFIX = '/wp-content/uploads/';

	/** @var bool Whether or not to load the current request remotely */
	private static $tryRemoteFallback = false;

	/**
	 * This method checks if we have the file on disk. If not, changes the domain of any requests for files within the
	 * uploads directory to the remote domain. It also sets a flag that this request is now a remote request.
	 *
	 * @param string $sitePath
	 * @param string $siteName
	 * @param string $uri
	 *
	 * @return bool|false|string
	 */
	public function isStaticFile( $sitePath, $siteName, $uri ) {

		$localFileFound = parent::isStaticFile( $sitePath, $siteName, $uri );

		if ( $localFileFound ) {
			return $localFileFound;
		}

		if ( self::stringStartsWith( $uri, self::URI_PREFIX ) ) {
			self::$tryRemoteFallback = true;

			return rtrim( self::REMOTE_HOST, '/' ) . $uri;
		}

		return false;
	}

	/**
	 * This method checks if the remote flag is set and, if so, redirects the request by setting the Location header.
	 *
	 * @param string $staticFilePath
	 * @param string $sitePath
	 * @param string $siteName
	 * @param string $uri
	 */
	public function serveStaticFile( $staticFilePath, $sitePath, $siteName, $uri ) {
		if ( self::$tryRemoteFallback ) {
			header( "Location: $staticFilePath" );
		} else {
			parent::serveStaticFile( $staticFilePath, $sitePath, $siteName, $uri );
		}
	}

	/**
	 * @param string $string
	 * @param string $startsWith
	 *
	 * @return bool
	 */
	private static function stringStartsWith( $string, $startsWith ) {
		return strpos( $string, $startsWith ) === 0;
	}

}

Hi,
I think this needs to be updated to work with Valet 4.0

I keep getting declaration errors on serverStaticFile Ln55