woocommerce email format string

woocommerce_email_format_string change string define in email

function tzn_custom_woocommerce_email_format_string($string, $email)
{
	$order = $email->object;
	$voucher = wc_pdf_product_vouchers_get_voucher( get_the_ID() );
	$value     = $voucher->get_product_price();
	$new_placeholders = array(
		'{amount_voucher}' => $value ,
	);
	return str_replace(array_keys($new_placeholders), array_values($new_placeholders), $string);
}

add_filter('woocommerce_email_format_string', 'tzn_custom_woocommerce_email_format_string', 20, 2);