PHP PDO Conditional Image ??

I'm trying to elarn PHP PDO - Not sure how to conditionally show the image (blog_img) :

I'm learning PHP PDO - How do you conditionally show an image based on whether it exists? I have the code below at the moment but if no image exists for an article then there's a placeholder for broken image link..

     Code:

     $ARTICLE = $conn->prepare("SELECT blog_title, blog_article, blog_img FROM Blog WHERE blog_title=:blog_title");

     $ARTICLE->bindParam(':blog_title', $blog_title, PDO::PARAM_STR, 25);

     $ARTICLE->execute();

   <?php

     while ($r = $ARTICLE->fetch()) {

     ?>

     <h1>

        <?PHP

    echo ($r['blog_title']);

      ?>

     </h1>

      <img src="images/<?PHP echo ($r['blog_img']);?>">

       <?PHP

       echo ($r['blog_article']);

       ?>

     <?php

      }

    ?>