public function getImage($attachment_id, $size = "post-thumbnail", $placeholder = true)
    {
        $sizes = $this->getConfig("image-sizes");

        if (isset($sizes[$size]) && $placeholder) {
            $image = "//placehold.it/" . $sizes[$size]["width"] . "x" . $sizes[$size]["height"];
        } else {
            $image = false;
        }

        $imgData = wp_get_attachment_image_src($attachment_id, $size);
        if ($imgData && is_array($imgData) && isset($imgData[0]) && $imgData[0]):
            $image = $imgData[0];
        endif;

        return $image;
    }