header.php

<div class="title-block center">
    
    <nav class="navbar navbar-expand-lg navbar-light" style="background-color: #DB636A;">

        <a class="navbar-brand" href="index.php">
        
        <img class="camarita" src="https://www.jing.fm/clipimg/full/0-1273_digital-camera-clipart-small-camera-camera-icon-transparent.png">
        
        </a>

        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false"
         aria-label="Toggle navigation">
            <span class="navbar-toggler-icon"></span>
        </button>

    <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav">
      
    <li class="nav-item">
        <a class="nav-link" href="index.php">Home</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="following.php">Following</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="trendings.php">Trendings</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="bootstrap.php">Bootstrap</a>
      </li>

      <form class="form-inline d-flex justify-content-center md-form form-sm mt-0">
        <i class="fa fa-search" aria-hidden="true"></i>
        <input class="form-control form-control-sm ml-3 w-75" type="text" placeholder="Search" aria-label="Search">
      </form>     
    </ul>
  </div>
</nav>
</div>