Display is not the same

in the displaying all items video the images are displayed from left to right but when i preview my code its from top to bottom can anyone figure out why

<?php

include('inc/data.php');

$pageTitle = "Full Catalog"; $section = null;

if(isset($_GET["cat"])){ if($_GET["cat"]== "books"){ $pageTitle = "Books"; $section = "books"; }else if($_GET["cat"] == "movies"){ $pageTitle = "Movies"; $section = "movies"; }else if($_GET["cat"] == "music"){ $pageTitle = "Music"; $section = "music"; } } include('inc/header.php'); ?>

<div class="section catalog page">

<div class= "wrapper">

<h1><?php echo $pageTitle; ?></h1>

<ul clas="items">

  <?php foreach($catalog as $item){
      echo "<li><a href='#'><img src ='"
          . $item["img"] . "' alt='"
          . $item["title"] . "' />" 
          . "<p> View Details</p>"
          . "</a></li>";

} ?>

</ul>

</div>

</div>

<?php include('inc/footer.php'); ?>