Data.php seems to have broken the site.

<?php 
include("inc/data.php");
include("inc/function.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 class="items" >
      <?php 
          foreach($catalog as $id => $item) {
          echo get_item_html($id,$item);
        }

       ?>


    </ul>

  </div>

</div>

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

<?php 
$catalog =  [];
$catalog[101] = [
  "title" => "Design Patterns",
  "img" => "img/media/design_patterns.jpg",
  "genre" => "Tech",
  "format" => "Paperback",
  "year" => 1994,
  "catagory" => "Books",
  "isbn" => "978*0201633610",
  "publisher" => "Prentice Hall",
  "authors" => [
    "Erich Gamma"
    "Richard Helm"
    "Ralph Johnson"
    "John Vlissides"
  ]
];
$catalog[102] = [
    "title" => "Clean Code: A Handbook of Agile Software Craftsmanship",
    "img" => "img/media/clean_code.jpg",
    "genre" => "Tech",
    "format" => "Ebook",
    "year" => 2008,
    "category" => "Books",
    "authors" => [
        "Robert C. Martin"
    ],
    "publisher" => "Prentice Hall",
    "isbn" => '978-0132350884'
];