public static function get_instance()
 {
     if (self::$instance === null) {
         self::$instance = new QHShop();
     }
     return self::$instance;
 }
Plugin Name: QH Shop plugin
Plugin URI:  http://come-stay.vn
Description: Plugin to create shop in wordpress
Version:     1.0
Author:      Jackie
Author URI:  http://come-stay.vn
Text Domain: qhshop
*/
// Make sure we don't expose any info if called directly
if (!function_exists('add_action')) {
    echo 'Hi there!  I\'m just a plugin, not much I can do when called directly.';
    exit;
}
define(QH_SHOP_VERSION, '1.0');
define(QH_SHOP_MINIMUM_VERSION, '4.1');
define(QH_SHOP_PLUGIN_DIR, plugin_dir_path(__FILE__));
define(QH_SHOP_PLUGIN_URL, plugin_dir_url(__FILE__));
define(QH_SHOP_PLUGIN_LANGUAGES, dirname(plugin_basename(__FILE__)) . 'languages');
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-session.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-product.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-order.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-setting.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-shortcode.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-tool.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-widget-cart.php';
require_once QH_SHOP_PLUGIN_DIR . 'includes/class.qhshop-widget-category.php';
register_activation_hook(__FILE__, array('plugin_activation'));
register_deactivation_hook(__FILE__, array('plugin_dectivation'));
QHShop::run();