Оператор SQL не получает определение переменной

В этом скрипте есть два оператора sql, первый обрабатывает все txt-поля, а PDO получает идентификатор строки:

$last_id = $conn->lastInsertId():

Второй sql-оператор находится внутри частного класса и должен вставить URL-адрес двух файлов в одну строку (как это делал первый оператор).

Первый SQL-запрос выполняется отлично. Второй - нет, и я думаю, потому что он не понимает, что такое $ last_id.

Любые предложения по работе второго PDO?

 <?php
require('../dbcon2.php');
//Connection 1
try {
        $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $stmt = $conn->prepare("INSERT INTO listings (title, address, lot_size, zoning, build_size, sale_price, lease_price, comment, transaction, date_added) VALUES (:title, :address, :lot_size, :zoning, :build_size, :sale_price, :lease_price, :comment, :transaction, now())");
          $stmt->bindParam(':title', $_POST['title']); 
          $stmt->bindParam(':address', $_POST['address']);
          $stmt->bindParam(':lot_size', $_POST['lot_size']);
          $stmt->bindParam(':zoning', $_POST['zoning']);
          $stmt->bindParam(':build_size', $_POST['build_size']);
          $stmt->bindParam(':sale_price', $_POST['sale_price']);
          $stmt->bindParam(':lease_price', $_POST['lease_price']);
          $stmt->bindParam(':comment', $_POST['comment']);
          $stmt->bindParam(':transaction', $_POST['transaction']);
        $stmt->execute();
        $last_id = $conn->lastInsertId();
}
catch(PDOException $e)
{
echo $sql . "<br>" . $e->getMessage();
}
 $conn = null;
 //Create class
    class CropAvatar {
        private $src;
        private $data;
        private $file;
        private $dst;
        private $type;
        private $extension;
        private $srcDir = '../0images/listimg/orig';
        private $dstDir = '../0images/listimg/mod';
        private $msg;

function __construct($src, $data, $file, $last_id) {
    $this -> setSrc($src);
    $this -> setId($last_id);
    $this -> setData($data);
    $this -> setFile($file);
    $this -> crop($this -> src, $this -> dst, $this -> data);
}
        private $last_id;
        public function setId($last_id) {
                 $this->id = $last_id;
}
        private function setSrc($src) {
            if (!empty($src)) {
                $type = exif_imagetype($src);
                if ($type) {
                    $this -> src = $src;
                    $this -> type = $type;
                    $this -> extension = image_type_to_extension($type);
                    $this -> setDst();
                }
            }
        }
        private function setData($data) {
            if (!empty($data)) {
                $this -> data = json_decode(stripslashes($data));
            }
        }
        private function setFile($file) {
            $errorCode = $file['error'];
            if ($errorCode === UPLOAD_ERR_OK) {
                $type = exif_imagetype($file['tmp_name']);
                if ($type) {
                    $dir = $this -> srcDir;
                    if (!file_exists($dir)) {
                        mkdir($dir, 0777);
                    }
                    $currdate=date('YmdHis');
                    $extension = image_type_to_extension($type);
                    $src = $dir . '/' . $currdate . $extension;
                    if ($type == IMAGETYPE_GIF || $type == IMAGETYPE_JPEG || $type == IMAGETYPE_PNG) {
                        if (file_exists($src)) {
                            unlink($src);
                        }
                        $result = move_uploaded_file($file['tmp_name'], $src);
                        $listing_img="http://www." . $Website . ".com/0images/listimg/mod/" . $currdate . $extension;
  //Process file upload 
                        $allowedExtsf = array("pdf");
                        $tempf = explode(".", $_FILES["flyer"]["name"]);
                        $extensionf = end($tempf);
                        if (($_FILES["flyer"]["type"] == "application/pdf")
                        && ($_FILES["flyer"]["type"] <2000000000)
                        && in_array($extensionf, $allowedExtsf)) 
                        {
                            $flyername=$_FILES["flyer"]["name"];
                            if ($_FILES["flyer"]["error"] > 0) 
                            {
                            echo "Return Code: " . $_FILES["flyer"]["error"] . "<br>";
                            }   
                                else 
                                {
                                    if (file_exists("../flyers/" . $_FILES["flyer"]["name"])) 
                                    {
                                     echo $_FILES["flyer"]["name"] . " already exists. ";
                                    }
                                        else 
                                        {
                                        move_uploaded_file($_FILES["flyer"]["tmp_name"],"../flyers/" . $_FILES["flyer"]["name"]);
                                         }
                                }
                        $ad_link="http://www." . $Website . ".com/flyers/" . $_FILES["flyer"]["name"];
      //Connection 2
      try {
          $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
          $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
          $sql="UPDATE listings SET ad_link='$ad_link', listing_img='$listing_img' WHERE id=$last_id";
          $conn->exec($sql);
          }
      catch(PDOException $e)
          {
          echo $sql . "<br>" . $e->getMessage();
          }
      $conn = null;
          }
      //Error handling
                        if ($result) {
                            $this -> src = $src;
                            $this -> type = $type;
                            $this -> extension = $extension;
                            $this -> setDst();
                        } else {
                             $this -> msg = 'Failed to save file';
                        }
                    } else {
                        $this -> msg = 'Please upload image with the following types: JPG, PNG, GIF';
                    }
                } else {
                    $this -> msg = 'Please upload image file';
                }
            } else {
                $this -> msg = $this -> codeToMessage($errorCode);
            }
        }

        private function setDst() {
            $dir = $this -> dstDir;

            if (!file_exists($dir)) {
                mkdir($dir, 0777);
            }

            $this -> dst = $dir . '/' . date('YmdHis') . $this -> extension;
        }

        private function crop($src, $dst, $data) {
            if (!empty($src) && !empty($dst) && !empty($data)) {
                switch ($this -> type) {
                    case IMAGETYPE_GIF:
                        $src_img = imagecreatefromgif($src);
                        break;

                    case IMAGETYPE_JPEG:
                        $src_img = imagecreatefromjpeg($src);
                        break;

                    case IMAGETYPE_PNG:
                        $src_img = imagecreatefrompng($src);
                        break;
                }

                if (!$src_img) {
                    $this -> msg = "Failed to read the image file";
                    return;
                }

                $dst_img = imagecreatetruecolor(220, 220);
                $result = imagecopyresampled($dst_img, $src_img, 0, 0, $data -> x, $data -> y, 220, 220, $data -> width, $data -> height);

                if ($result) {
                    switch ($this -> type) {
                        case IMAGETYPE_GIF:
                            $result = imagegif($dst_img, $dst);
                            break;

                        case IMAGETYPE_JPEG:
                            $result = imagejpeg($dst_img, $dst);
                            break;

                        case IMAGETYPE_PNG:
                            $result = imagepng($dst_img, $dst);
                            break;
                    }

                    if (!$result) {
                        $this -> msg = "Failed to save the cropped image file";
                    }
                } else {
                    $this -> msg = "Failed to crop the image file";
                }

                imagedestroy($src_img);
                imagedestroy($dst_img);
            }
        }
        private function codeToMessage($code) {
            switch ($code) {
                case UPLOAD_ERR_INI_SIZE:
                    $message = 'The uploaded file exceeds the upload_max_filesize directive in php.ini';
                    break;

                case UPLOAD_ERR_FORM_SIZE:
                    $message = 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form';
                    break;

                case UPLOAD_ERR_PARTIAL:
                    $message = 'The uploaded file was only partially uploaded';
                    break;

                case UPLOAD_ERR_NO_FILE:
                    $message = 'No file was uploaded';
                    break;

                case UPLOAD_ERR_NO_TMP_DIR:
                    $message = 'Missing a temporary folder';
                    break;

                case UPLOAD_ERR_CANT_WRITE:
                    $message = 'Failed to write file to disk';
                    break;

                case UPLOAD_ERR_EXTENSION:
                    $message = 'File upload stopped by extension';
                    break;

                default:
                    $message = 'Unknown upload error';
            }

            return $message;
        }

        public function getResult() {
            return !empty($this -> data) ? $this -> dst : $this -> src;
        }

        public function getMsg() {
            return $this -> msg;
        }
    }
$crop = new CropAvatar($_POST['avatar_src'], $_POST['avatar_data'], $_FILES['avatar_file'], $last_id);
    $response = array(
        'state'  => 200,
        'message' => $crop -> getMsg(),
        'result' => $crop -> getResult()
    );
    echo json_encode($response);
?>