On the Shipping Information page, when a phone number is provided that has an area code greater than "214", after the "continue on to billing" button is clicked, the following error results: "An error occurred in script 'C:\wamp64\www\effortlessECommerce\effortless_ecommerce_2nd\ex2\html\checkout.php' on line 158: Your order could not be processed due to a system error."
This is because the add_customer stored procedure's "p" (aka "phone") parameter is stored as an "int", and ints have a maximum value of 2,147,483,647. Therefore, a phone number with an area code larger than 214 will fail.