Handling PHP Form Postbacks: Same-Page Validation
Assuming a form will have problems allows you to more easily build validation routines.
Tag: radio buttons
How To Increment A Counter In MySQL Based On A Radio Button Click
You want to count how many times an element on your page was clicked. There's two ways to do it: with a PHP postback and, of course, via JavaScript with an AJAX...
Working With authorize.net Server Integration Method (SIM) Payment Gateway, Part 2: Proper Form Design
The most important step in using the authorize.net payment gateway is properly designing your ordering system / shopping cart first.
Working With The authorize.net Server Integration Method (SIM) Payment Gateway, Part 1: Don’t Use JavaScript
JavaScript is too insecure to compute shopping cart totals. You can't rely on it when submitting payment requests to authorize.net.