Processing form data in PHP is significantly simpler than most other Web programming languages. This simplicity and ease of use makes it possible to do some fairly complex things with forms ...

When a user submits an HTML form, the Web page reloads and the information the user entered into the form is no longer displayed. To avoid the perception that this information was lost, you can ...

The HTML form passes key-value pairs to PayPal in a "variable=value" format; you are required to pass a specific action URL and some input fields.