Create PHP script for PayPal authorize and capture transactions

I need a PHP script that processes payments using authorize and capture method with PayPal. We're creating a system where users can make appointments. The total cost of the appointment is known in advance of the appointment date. The system needs to authorize this amount up front. Once the appointment is complete, we need to capture the payment for the appointment. Script should: 1) accept a payment amount and an appointment id then redirect to paypal where user can enter their payment information. For example: authorizePaymentForAppointment($amount, $apptId) - if the authorization is successful, send the transaction information and appointment id back to the site by calling: saveTransactionForAppointment($transactionId, $authorizationId, $apptId) - if the user cancels the transaction or fails authorization, send the appointment id back to the site by calling: cancelTransactionForAppointment($apptId) 2) accept request to capture the authorized amount. For example: capturePaymentForAppointment($apptId,$authorizationId,$amount) - send the results of the request by calling updatePaymentForAppointment($apptId, $status) 3) accept request to void the authorization. For example: voidAuthorization($authorizationId) Here is a link with information about the PayPal API. [login to view URL]