PHP & Database Development

We have a live site that sell tickets to customers, we recently had an update, but the developer left it with a number of errors, currently a few of those errors are more urgent than the others, If we can have these fix effectively then it will lead to more work on the site. The Details of immediate require fix When a customer books a ticket, the site no longer updates the records to subtract the ticket. From the available tickets. the customer should also receive a confirmation email with his booking details and Eticket (if available) after the transaction is completed on the gateway but this is no longer working. We believe the introduction of the promo code facility have corrupted this functionality – the promo code allows a customer to book a ticket for free or at a discounted price. When the promo code is used then the site functions normal and customer receives his confirmation email In addition if we makes any changes in the admin to the ticket on sale, the amount of tickets available are reset to the original amount despite what was previously sold. But does not affect the orders record in the database. However, this error make more tickets available In the confirmation email that the customer receives there is URL link that displays the Eticket. The Eticket contains a QR code which when scanned display the customers detail, If we cancel a ticket although it removes it from the database, it does not update the QR Code records so the ticket still appears as valid. we also need a checked button added to the details when scanned. so, we can mark the ticket as used when a customer presents it for entry We also need a more secure URL for the Eticket access