Track 404 Not Found errors for page that don't exist

Add code to set the page title to include information about the
URL and referrer for pages that do not exist. Based on
recommendations at https://matomo.org/faq/how-to/faq_60/

Also fix some minor phpdoc syntax.

Bug: DaSchTour#46

src/Hooks.php

@@ -3,6 +3,8 @@
 namespace MediaWiki\Extension\Matomo;
 
 use RequestContext;
+use Skin;
+use Title;
 use Xml;
 
 class Hooks {
@@ -19,7 +21,7 @@ class Hooks {
 	/**
 	 * Initialize the Matomo hook
 	 *
-	 * @param string $skin
+	 * @param Skin $skin
 	 * @param string &$text
 	 * @return bool
 	 */
@@ -77,7 +79,7 @@ public static function onSpecialSearchSetupEngine( $search, $profile, $engine )
 
 	/**
 	 * Add Matomo script
-	 * @param string $title
+	 * @param Title $title
 	 * @return string
 	 */
 	public static function addMatomo( $title ) {
@@ -185,6 +187,15 @@ public static function addMatomo( $title ) {
 
 		}
 
+		$track404s = '';
+		if ( !$title->exists() ) {
+			$track404s = "_paq.push(["
+				. "'setDocumentTitle',"
+				. "'404/URL = ' +  encodeURIComponent(document.location.pathname+document.location.search)"
+				. " + '/From = ' + encodeURIComponent(document.referrer)"
+				. "]);";
+		}
+
 		// Prevent XSS
 		$finalActionName = Xml::encodeJsVar( $finalActionName );
 
@@ -205,6 +216,7 @@ public static function addMatomo( $title ) {
 <!-- Matomo -->
 <script type="text/javascript">
   var _paq = _paq || [];{$disableCookiesStr}{$customJs}
+  {$track404s}
   _paq.push(["{$trackingType}"{$jsTrackingSearch}]);
   _paq.push(["enableLinkTracking"]);