Modified headers of error pages.

errors/403.php

@@ -1,5 +1,5 @@
 <?php
-http_response_code(403);
+header('HTTP/1.1 403 Forbidden', true, 403);
 ?>
 <div class="container">
     <div class="row">
@@ -17,4 +17,4 @@ http_response_code(403);
             </div>
         </div>
     </div>
-</div>
+</div>

errors/404.php

@@ -1,5 +1,5 @@
 <?php
-http_response_code(404);
+header('HTTP/1.1 404 Not Found', true, 404);
 ?>
 <div class="container">
     <div class="row">
@@ -17,4 +17,4 @@ http_response_code(404);
             </div>
         </div>
     </div>
-</div>
+</div>