fixed multiple things

public/update_lessonnotification.php

@@ -0,0 +1,35 @@
+<?php
+require_once('Connections/bkngstm.php');
+
+$conn = new mysqli($servername, $username, $password, $dbname);
+
+if ($conn->connect_error) {
+    die(json_encode(['success' => false, 'error' => 'Connessione fallita: ' . $conn->connect_error]));
+}
+
+if (isset($_POST['userid']) && isset($_POST['lessonnotification'])) {
+    $userid = $_POST['userid'];
+    $lessonnotification = $_POST['lessonnotification'];
+
+    // Validate lessonnotification value
+    if (!in_array($lessonnotification, ['Y', 'N'])) {
+        echo json_encode(['success' => false, 'error' => 'Valore lessonnotification non valido']);
+        exit;
+    }
+
+    $query = "UPDATE auth_users SET lessonnotification = ? WHERE id = ?";
+    $stmt = $conn->prepare($query);
+    $stmt->bind_param("si", $lessonnotification, $userid);
+
+    if ($stmt->execute()) {
+        echo json_encode(['success' => true]);
+    } else {
+        echo json_encode(['success' => false, 'error' => $conn->error]);
+    }
+
+    $stmt->close();
+} else {
+    echo json_encode(['success' => false, 'error' => 'Parametri mancanti']);
+}
+
+$conn->close();