Gravity Forms Duplicate Prevention

This plugin adds silent duplicate detection to the popular Gravity Forms WordPress plugin. The goal is to prevent Gravity Forms from creating multiple entries when an impatient user double-, triple, or full-on secret-combo-move-clicks his/her mouse when submitting a form. No modifications to your forms is necessary, it just works.

How does it work?

The plugin prevents duplicate submissions in two ways: first, a small bit of JavaScript is loaded into the page that disables the submit button(s) on form submit. Second, the plugin creates a cryptographic hash of the form data upon submission. This unique hash is compared to a hash stored in a PHP session (if available) and, if a matching hash is found, the form data is altered to simulate a failing honeypot condition. Like with all failed honeypots, Gravity Forms will skip saving the data or sending any notifications but the form will appear (to the user) to have been submitted successfully.

Plugin development can be tracked on the project’s Github Page: https://github.com/buckii/gravity-forms-duplicate-prevention

1. Upload the gravity-forms-duplicate-prevention plugin to your WordPress plugins directory
2. Activate the plugin

What versions of Gravity Forms has this plugin been tested against?

The plugin was developed against Gravity Forms version 1.6.11, the most current at the time. If you find issues with newer versions please file a bug report at https://github.com/buckii/gravity-forms-duplicate-prevention.

Can I prevent loading the client-side scripting?

Yes! The JavaScript file is a very simple jQuery-powered event listener. If you’d prefer to move it to your own script file (or exclude it entirely), you can add the following to your theme’s functions.php:

add_filter( 'gform_duplicate_prevention_load_script', '__return_false' );

I find your lack of paranoia disturbing. What if your plugin accidentally honeypots a valid submission?

We’d by lying if I said that didn’t happen to us in testing. As a result we’ve ensured that Gravity Forms Duplicate Prevention will log the raw HTTP POST data upon detection of a duplicate entry (sent through PHP’s system logger using error_log). If something goes wrong your data should be recoverable.

As of version 0.1.1 you can also latch onto the gform_duplicate_prevention_duplicate_entry action hook if you want to do anything else with the duplicate data; Your function will receive the $validation_result array as it was passed to the plugin by Gravity Forms’ gform_validation filter.

Example:

function log_duplicate_entries( $validation_result ) {
  // send an email, log it, and/or add points to the user's double-click combo score here
}
add_action( 'gform_duplicate_prevention_duplicate_entry', 'log_duplicate_enties' );

How can I contribute to the further development of this plugin?

The plugin’s source is hosted on Github: https://github.com/buckii/gravity-forms-duplicate-prevention. If you’d like to contribute, please feel free to send us a pull request or contact us there.

0.1.5

• Add credit card number obfuscation (thanks Justin Foell) and gform_duplicate_prevention_execute filter (thanks Mat Gargano).

0.1.4

• Integrate Gravity Forms logging support (thanks Justin Foell).

0.1.3

• Limit the scope of the JavaScript button disabling to submit buttons within .gform_wrapper elements (thanks to Mike Yott for catching this!)

0.1.2

• Fixed strict notices regarding the plugin version

0.1.1

• Added gform_duplicate_prevention_duplicate_entry action hook that fires when a duplicate entry is detected
• Documentation updates

0.1

• First public version of the plugin