I am getting a PDO error when trying to push my PHP application that uses a database to Heroku. Everything with the app works fine on cloud9 (online ide), but when it is pushed then an error is thrown. Below you will see the error logs from Heroku. Any ideas of how I can troubleshoot this?

2018-05-28T18:29:08.526557+00:00 app[web.1]: thrown in /app/database.php on line 17

2018-05-28T18:29:08.526876+00:00 app[web.1]: 10.79.229.184 - - [28/May/2018:18:29:08 +0000] "GET / HTTP/1.1" 500 - "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36

2018-05-28T18:29:08.923554+00:00 app[web.1]: [28-May-2018 18:29:08 UTC] PHP Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2002] No such file or directory' in /app/database.php:17

2018-05-28T18:29:08.923715+00:00 app[web.1]: #0 /app/database.php(17): PDO->__construct('mysql:host=;dbn...', NULL, NULL)

2018-05-28T18:29:08.923574+00:00 app[web.1]: Stack trace:

2018-05-28T18:29:08.923825+00:00 app[web.1]: #1 /app/index.php(31): getDatabaseConnection()

2018-05-28T18:29:08.923834+00:00 app[web.1]: #2 {main}

2018-05-28T18:29:08.923902+00:00 app[web.1]: thrown in /app/database.php on line 17

2018-05-28T18:29:08.924281+00:00 app[web.1]: 10.79.229.184 - - [28/May/2018:18:29:08 +0000] "GET / HTTP/1.1" 500 - "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36

2018-05-28T18:29:08.922514+00:00 heroku[router]: at=info method=GET path="/" host=protected-scrubland-18991.herokuapp.com request_id=6a972e81-f5e0-4011-8a3b-9012e07a6617 fwd="198.189.249.57" dyno=web.1 connect=0ms service=2ms status=500 bytes=306 protocol=https

The code the error is referring to is the script below AND refers to line 17:

Line 17: $dbConn = new PDO("mysql:host=$host;dbname=$dbname", $username, $password);

Rest of the code:

setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); return $dbConn; }

function insertItemsIntoDB($items) { if (!$items){ return; } $db = getDatabaseConnection(); foreach ($items as $item) { $itemName = $item['name']; $itemPrice = $item['salePrice']; $itemImage = $item['thumbnailImage']; $sql = "INSERT INTO item (item_id, name, price, image_url) VALUES (NULL, :itemName, :itemPrice, :itemURL)"; $statement = $db->prepare($sql); $statement->execute(array( itemName => $itemName, itemPrice => $itemPrice, itemURL => $itemImage)); } } function getMatchingItems($query, $category, $priceFrom, $priceTo, $ordering, $showImages) { $db = getDatabaseConnection(); $imgSQL = $showImages ? ', item.image_url' : ''; $sql = "SELECT DISTINCT item.item_id, item.name, item.price $imgSQL FROM item INNER JOIN item_category ON item.item_id = item_category.item_id INNER JOIN category ON item_category.category_id =category.category_id WHERE 1"; if(!empty($query)) { $sql .= " AND item.name LIKE '%$query%'"; } if (!empty($category)) { $sql .= " AND category.category_name = '$category'"; } if (!empty($priceFrom)) { $sql .= " AND item.price >= '$priceFrom'"; }

if (!empty($priceTo)) { $sql .= " AND item.price <= '$priceTo'"; } if (!empty($ordering)) { if ($ordering == 'product') { $columnName = 'item.name'; } else { $columnName = 'item.price'; } $sql.= " ORDER BY $columnName"; } $statement = $db->prepare($sql); $statement->execute(); $items = $statement->fetchAll(); return $items; } function getCategoriesHTML() { $db = getDatabaseConnection(); $categoriesHTML = ""; // User can opt to not select a category $sql = "SELECT category_name FROM category"; $statement = $db->prepare($sql); $statement->execute(); $records = $statement->fetchAll(PDO::FETCH_ASSOC); foreach ($records as $record) { $category = $record['category_name']; $categoriesHTML .= "$category"; } return $categoriesHTML; } function addCategoriesForItems($itemStart, $itemEnd, $category_id) { $db = getDatabaseConnection(); for ($i = $itemStart; $i <= $itemEnd; $i++) { $sql = "INSERT INTO item_category (grouping_id, item_id, category_id) VALUES (NULL, '$i', '$category_id')"; $db->exec($sql); } } ?>