header.php

<nav class="navbar navbar-expand-lg navbar-light" style="background-color: #8762a3; color: black;">

  <a class="navbar-brand" href="http://localhost/resultify/login.php">Results</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent"
    aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>

  <div class="collapse navbar-collapse" id="navbarSupportedContent">
    <ul class="navbar-nav ml-auto">

      <li class="nav-item">
        <button class="nav-link" onclick="window.print()" >Click Me</button>
      </li>
      <!-- <li class="nav-item">
        <button class="nav-link" onclick="savePDF()" >Generate PDF</button>        
      </li> -->
      <li class="nav-item">
        <a class="nav-link" href="login.php">Log Out</a>
      </li>
    </ul>
  </div>

</nav>