Solution 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
   "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
     <title>Animal Gallery</title>
  </head>
  <body>
    <div>
      <?php
      $animal = "";
      if (isset($_REQUEST["animal"])) {
          $animal = $_REQUEST["animal"];
      }
      $files = glob("images/{$animal}*.jpeg");
      foreach ($files as $image) {
         ?>
         <img src="<?= $image ?>" alt="animal picture" />
         <?php
      }
      ?>
    </div>
  </body>
</html>