Fix bug in and add validity check in MDObjectSyndicationSet

src/MDObjectSyndicationSet.php

@@ -39,7 +39,7 @@ final class MDObjectSyndicationSet extends MDValueSet {
      *
      * @return string
      */
-    public function getSearchUrlForObject(string $repo, string $instId, string $search_value):string {
+    public static function getSearchUrlForObject(string $repo, string $instId, string $search_value):string {
 
         switch ($repo) {
         case 'ddb':
@@ -50,6 +50,22 @@ final class MDObjectSyndicationSet extends MDValueSet {
 
     }
 
+    /**
+     * Function for checking the availability of a provided repository in the
+     * list of known repositories.
+     *
+     * @param string $repo Repository name to check.
+     *
+     * @return string|boolean
+     */
+    final public static function checkRepositoryIsKnown(string $repo) {
+        if (isset(self::REPOSITORIES[$repo])) {
+            return self::REPOSITORIES[$repo];
+        }
+        return false;
+
+    }
+
     /**
      * Gets a sorted list of the entries in a translated version.
      *