Data Validation for Coupon Codes

Gravity Forms doesn't do this out of the box as it's more specialized functionality.

HOWEVER thats why we have API hooks/filters so you can customize the functionality without changing the core plugin code and make it do what you want to do.

The gform_validation hook is used to apply custom validation to a field. You can use this hook to interact with the Groupon API and validate the coupon code.

Here is an example of using the gform_validation hook:

<?php
add_filter('gform_validation', 'custom_validation');
function custom_validation($validation_result){

// set the form validation to false
$validation_result["is_valid"] = false;
$form = $validation_result["form"];

// specify the first field to be invalid and provide custom validation message
$form["fields"][0]["failed_validation"] = true;
$form["fields"][0]["validation_message"] = "This field is invalid!";

// update the form in the validation result with the form object you modified
$validation_result["form"] = $form;

return $validation_result;

}
?>

So this isn't something Gravity Forms does out of the box but you can write code using the gform_validation hook to implement this functionality.

If they provide you with this information you could create your own database table and validate against that. With the gform_validation hook you could do virtually anything because it's custom PHP that you can write. So yes, you could do this.

If this is outside the scope of your skill set i'd be glad to refer you to a WordPress consultant with Gravity Forms customization experience who could assist you with this. I already know one who has done coupon functionality so similar functionality has been done before.

We will be launching new developer documentation that will document (with examples) all of the available hooks and filters by the end of next week when we launch our new web site and the Gravity Forms v1.5 public release.