mobile.php

<nav class="navbar navbar-dark bg-gradient-facebook px-4 col-12 d-md-none">
    <a class="navbar-brand mr-lg-5" href="index.html">
        <img class="navbar-brand-dark" src="assets/img/logo.png">
        <img class="navbar-brand-light" src="assets/img/logo.png">
    </a>
    <div class="d-flex align-items-center">
        <button class="navbar-toggler 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>
    </div>
</nav>