What causes an error when calling the order invoice send mutation in PHP?

Shopify Discussion
1

Hi,

When call the order invoice send mutation using PHP below error occurs, anyone know the issue?

syntax error, unexpected STRING ("gid://shopify/Order/5488831299859"), expecting VAR_SIGN at [1, 31

code segment is like below

$orderId = '"gid://shopify/Order/5488831299859"';
        $email = '"udara.itplace@gmail.com"';
        $query = <<