Functions Return "Unable to Retrieve Results" Error

<?php
function full_catalog_array() {
  include("connection.php");

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

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

function random_catalog_array() {
  include("connection.php");

  try {
    $results = $db->query(
    "SELECT Media.media_id, title, category, img
    FROM Media
    ORDER BY RANDOM()
    LIMIT 4");
  } catch (Exception $e){
    echo "Unable to retrieve results";
    exit;
  }

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


function single_item_array($id) {
  include("connection.php");

  try {
    $results = $db->prepare("SELECT Media.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 = ?"
    );
    $results->bindParam(1, $id, PDO::PARAM_INT);
    $results->execute();
  } catch (Exception $e){
    echo "Unable to retrieve results";
    exit;
  }

  $item = $results->fetch(PDO::FETCH_ASSOC);
  if (empty($item)) return $item; // Early return
  try {
    $results = $db->prepare("SELECT fullname, role
      FROM Media_People
      JOIN People ON Media.People.people_id = People.people_id
      WHERE Media_People.media_id = ?"
    );
    $results->bindParam(1, $id, PDO::PARAM_INT);
    $results->execute();
  } catch (Exception $e){
    echo "Unable to retrieve results";
    exit;
  }
  while($row = $results->fetch(PDO::FETCH_ASSOC)) {
    $item[$row["row"]][] = $row["fullname"];
  }
  return $item;
}

function get_item_html($item) {
  $output = "<li><a href='details.php?id="
    . $item["media_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);
}