fixed redirect and error message on add_user dialog

app/public/add_user.php

@@ -3,6 +3,7 @@
     include("../scripts/connection.php");
     include("../scripts/functions.php");
     $user_data = check_admin($con);
+    $error = null;
 
     if($_SERVER['REQUEST_METHOD'] == "POST") {
         $user_name = $_POST['user_name'];
@@ -18,8 +19,10 @@
             } else {
                 write_user($con, $user_name, $user_id, $phash, $salt, $user_group, NULL);
             }
+            header("Location: manage_user.php");
+            die;
         } else {
-            echo "Bitte Benutzername und Passwort eintragen!";
+            $error = "Bitte Benutzername und Passwort eintragen!";
         }
     }
 
@@ -32,6 +35,7 @@
     </div>
     <div>
         <form method="post">
+            <label><?php echo $error ?></label><br>
             <label for="user_name">Benutzername</label>
             <input type="text" name="user_name"/><br>
             <label for="password">Passwort</label>