Added (Check Duplicates Before Adding New User)

header.php

@@ -0,0 +1,12 @@
+<?php
+// Define default config values
+$defaultConfig = [
+    'chap_secrets_path' => '/etc/ppp/chap-secrets',
+    'admin_username' => 'admin',
+    'admin_password' => password_hash('change@me', PASSWORD_DEFAULT),
+];
+
+// Create config.php if it doesn't exist
+if (!file_exists('config.php')) {
+    file_put_contents('config.php', '<?php return ' . var_export($defaultConfig, true) . ';');
+}

index.php

@@ -1,16 +1,6 @@
 <?php
+include 'header.php';
 session_start();
-// Define default config values
-$defaultConfig = [
-    'chap_secrets_path' => '/etc/ppp/chap-secrets',
-    'admin_username' => 'admin',
-    'admin_password' => password_hash('change@me', PASSWORD_DEFAULT),
-];
-
-// Create config.php if it doesn't exist
-if (!file_exists('config.php')) {
-    file_put_contents('config.php', '<?php return ' . var_export($defaultConfig, true) . ';');
-}
 
 if (!isset($_SESSION['loggedin']) || $_SESSION['loggedin'] !== true) {
     header('Location: login.php');

login.php

@@ -1,4 +1,6 @@
 <?php
+include 'header.php';
+
 session_start();
 
 if ($_SERVER['REQUEST_METHOD'] === 'POST') {