session_start wird nun vorher geprüft, ob diese schon läuft

php/controller/createArticle-controller.php

@@ -1,5 +1,7 @@
 <?php
-SESSION_START();
+if (session_status() === PHP_SESSION_NONE) {
+    session_start();
+}
 require_once '../model/LocalArticleManager.php';
 require_once '../model/ArticleManager.php';
 require_once '../validator/article-validator.php';

php/controller/home-controller.php

@@ -1,5 +1,7 @@
 <?php
-session_start();
+if (session_status() === PHP_SESSION_NONE) {
+    session_start();
+}
 require_once 'php/model/Article.php';
 require_once 'php/model/ArticleManager.php';
 require_once 'php/model/LocalArticleManager.php';

php/controller/search-results-controller.php

@@ -1,5 +1,7 @@
 <?php
-session_start();
+if (session_status() === PHP_SESSION_NONE) {
+    session_start();
+}
 require_once '../model/LocalArticleManager.php';
 require_once '../model/ArticleManager.php';
 require_once '../model/Article.php';

php/controller/showArticle-controller.php

@@ -1,5 +1,8 @@
 <?php
-session_start();
+if (session_status() === PHP_SESSION_NONE) {
+    session_start();
+}
+
 require_once 'php/model/Article.php';
 require_once 'php/model/ArticleManager.php';
 

php/controller/updateArticle-controller.php

@@ -1,5 +1,8 @@
 <?php
-SESSION_START();
+if (session_status() === PHP_SESSION_NONE) {
+    session_start();
+}
+
 require_once '../model/LocalArticleManager.php';
 require_once '../model/ArticleManager.php';
 require_once '../model/Article.php';

php/validator/article-validator.php

@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Prüft, ob der Autor auch der Eigentümer des Beitrags ist.
  * @param $author