add this to git finally

header.php

@@ -0,0 +1,40 @@
+<header>
+    <nav class="nav-links">
+        <a href="/users">Users</a>
+        <a href="/products">Products</a>
+        <a href="/orders">Orders</a>
+    </nav>
+
+    <div class="auth-section">
+        <?php
+        session_start(); if(isset($_SESSION['username']) && !empty($_SESSION['username'])): ?>
+        <div class="user-info">
+            <span class="username">Welcome, <?=htmlspecialchars($_SESSION['username'])?></span>
+            <a href="/logout" class="logout-link">Log out</a>
+        </div>
+        <?php else: ?>
+        <?php if (isset($_SESSION['error_message'])): ?>
+            <p style="color: red; text-align: center;"><?= $_SESSION['error_message'] ?></p>
+        <?php endif; ?>
+        <form id="authenticate-form" action="/login" method="post">
+            <input type="text" name="username" placeholder="Username (*for registration*)">
+            <input type="text" name="email" placeholder="Email" required>
+            <input type="password" name="password" placeholder="Password" required>
+            <button type="button" onclick="submitForm('login');">Login</button>
+            <button type="button" class="register-btn" onclick="submitForm('register');">Register</button>
+        </form>
+        <script>
+        function submitForm(action) {
+            const form = document.getElementById('authenticate-form');
+
+            form.action = `/${action}`;
+            if (form.checkValidity()) {
+                form.submit();
+            } else {
+                form.reportValidity();
+            }
+        }
+        </script>
+        <?php endif; ?>
+    </div>
+</header>