Unable to retrieve results

<?php

function full_catalog_array() {
  include("connection.php");
  try {
    $results = $db->query("SELECT media_id, title, category, img FROM Media");
  } catch (Exception $e) {
    echo "Unable to retrieve results";
    exit;
  }

  $catalog = $results->fetchAll();
  return $catalog;
}

function single_item_array($id) {
  include("connection.php");
  try {
    $results = $db->query(
      "SELECT media_id, title, category, img, format, year, genre, publisher, isbn 
      FROM Media
      JOIN Genres ON Media.genre_id = Genres.genre_id
      LEFT OUTER JOIN Books ON Media.media_id = Books.media_id
      WHERE Media.media_id = $id"
    );
  } catch (Exception $e) {
    echo "Unable to retrieve results";
    exit;
  }

  $catalog = $results->fetch();
  return $catalog;
}

var_dump(single_item_array(1));

function get_item_html($id,$item) {
    $output = "<li><a href='details.php?id="
        . $id . "'><img src='" 
        . $item["img"] . "' alt='" 
        . $item["title"] . "' />" 
        . "<p>View Details</p>"
        . "</a></li>";
    return $output;
}

function array_category($catalog,$category) {
    $output = array();

    foreach ($catalog as $id => $item) {
        if ($category == null OR strtolower($category) == strtolower($item["category"])) {
            $sort = $item["title"];
            $sort = ltrim($sort,"The ");
            $sort = ltrim($sort,"A ");
            $sort = ltrim($sort,"An ");
            $output[$id] = $sort;            
        }
    }

    asort($output);
    return array_keys($output);
}