header.php

<!-- Navbar -->
<nav class="navbar navbar-dark sticky-top flex-md-nowrap p-0 shadow img-nav">
    <a class="navbar-brand col-md-3 col-lg-2 mr-0 px-3" href="#">Hello <?= $_SESSION['username'] ?></a>
    <button class="navbar-toggler position-absolute d-md-none collapsed" type="button" data-toggle="collapse" data-target="#sidebarMenu" aria-controls="sidebarMenu" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>
    <ul class="navbar-nav px-3">
        <li class="nav-item text-nowrap">
            <a class="nav-link" href="logout.php">Sign out</a>
        </li>
    </ul>
</nav>

<div class="container-fluid">
    <div class="row">
        <nav id="sidebarMenu" class="col-md-3 col-lg-2 d-md-block bg-light sidebar collapse">
            <div class="sidebar-sticky pt-3">
                <ul class="nav flex-column">
                    <li class="nav-item">
                        <a class="nav-link" href="user_dashboard.php">
                            <span class="fas fa-home fa-fw mr-2"></span>
                            Dashboard <span class="sr-only">(current)</span>
                        </a>
                    </li>
                    <li class="nav-item">
                        <a class="nav-link" href="user_profile.php">
                            <span class="fa fa-user fa-fw mr-2"></span>
                            User
                        </a>
                    </li>
                </ul>
            </div>
        </nav>
    </div>
</div>
<!-- End Sidebar -->