Ошибка, на одном хосте php 5.6 работает, на другом нет, как исправить?

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<b>Notice</b>:  Undefined variable: client_email in <b>/var/www/data/www/site/controllers/ajax/user/_insertmkassaCtrl.php</b> on line <b>21</b><br />
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<b>Notice</b>:  Undefined variable: debug in <b>/var/www/data/www/site/controllers/ajax/user/_insertmkassaCtrl.php</b> on line <b>21</b><br />
{"status":"success","text":"<center><a href=\"https:\/\/megakassa.ru\/merchant\/?shop_id=3365&order_id=183&amount=45&currency=RUB\n\t&description=Balance&signature=\u043e\u043f\u043b\u0430\u0442\u0435<\/a><\/center>"}

$signature		= md5($secret_key.md5(join(':', array($shop_id, $amount, $currency, $description, $order_id, $method_id, $client_email, $debug, $secret_key))));