navbar.php

    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
 
    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"></script>
    <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"></script>
  
  <nav class="navbar navbar-expand-lg navbar-light" style="background-color: #e3f2fd;">
  <a class="navbar-brand" href="http://localhost:8080/index.php">Master of Wedding Pty Ltd</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavAltMarkup" aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
  <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" id="navbarNavAltMarkup">
  <div class="navbar-nav">
  <a class="nav-item nav-link active" href="http://localhost:8080/index.php">Home <span class="sr-only">(current)</span></a>
  <a class="nav-item nav-link" href="http://localhost:8080/product/product.php">Products</a>
  <a class="nav-item nav-link" href="http://localhost:8080/client/client.php">Clients</a>
  <a class="nav-item nav-link" href="http://localhost:8080/category/category.php">Categories</a>
  <?php if (!isset($_SESSION['user_id'])) { ?>
 
  <form class="form-inline">
  <a class="btn btn-primary" href="http://localhost:8080/login.php" role="button">Login</a>
  </form>

  <?php
  } else { ?>

  <form class="form-inline">
  <a class="btn btn-primary" href="http://localhost:8080/logout.php" role="button">Logout</a>
  </form>
 
  <?php
  } ?>

  </div>
  </div>
  </nav>