I have carousel image slider but it's not working

I am trying to show a dynamic image slider with the help of carousel slider but it's not working.

My code:

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.0/js/bootstrap.min.js"></script>
<section>
  <div class="container-fluid pt-70 pb-0">
  <div class="container">
    <div id="myCarousel" class="carousel slide" data-ride="carousel">
  <?php foreach ($gallery_imgs as $img):?> 
      <div class="carousel-inner">
        <div class="item">
          <img src="<?php echo base_url(); echo $img['thumbnail_url']; ?>" alt="Los Angeles" style="width:30%;">
        </div>
      </div>
    <?php endforeach;?>

      <!-- Left and right controls -->
      <a class="left carousel-control" href="#myCarousel" data-slide="prev">
        <span class="glyphicon glyphicon-chevron-left"></span>
        <span class="sr-only">Previous</span>
      </a>
      <a class="right carousel-control" href="#myCarousel" data-slide="next">
        <span class="glyphicon glyphicon-chevron-right"></span>
        <span class="sr-only">Next</span>
      </a>
    </div>
  </div>
  </div>
</section>

I do not know where I am wrong in my code.