Dynamic form specific hooks for GravityForms

I really like using GravityForms to create highly dynamic forms. The form builder offer a wide range of possibilities. But sometimes you need to use some code to hook into parts of the form processing. In this blog post I want to show you how to make this work even across multiple installations of a form.

Using a hook for all instances

Let’s take the gform_pre_submission as an example. If you want to hook into it, you would do as with any other hook in WordPress:

function my_pre_submission( $form ) {
    $_POST['input_1'] = 'updates value for field with ID 1';
add_action( 'gform_pre_submission', 'my_pre_submission' );

This code snippet would update every form field with ID 1 on every form. This is probably not what you want to do.

Using a hook for only one form

When changing a value, you usually do that for a specific form. This can be done by adding the form ID to the end of the hook:

function my_pre_submission( $form ) {
    $_POST['input_1'] = 'updates value for field with ID 1';
add_action( 'gform_pre_submission_1', 'my_pre_submission' );

Now, the value only get updated when the form with ID 1 is submitted. That could be a good solution, until you export/import your forms.

Handling different form IDs

Let’s say you have created a form for one project, and now you want to use it in another project. You can imply use the export/import of forms to copy over all settings of a form (without the entries). But if your other project already has forms, then your imported form might have a different ID on this new project. The same could happen, if you copy the form from a development environment to a live site, or if you are not the only one creating new forms.

In this case, you would have to find out your new form ID and change the values for the hooks. But what if you have these hooks in version control, and you can’t change it to a new static value?

Using a constant for the form ID

In a project with this issue, I’ve decided to use constants to store the form IDs. All hooks now look something like this:

function my_pre_submission_contact( $form ) {
    $_POST['input_1'] = 'updates value for field with ID 1';
add_action( 'gform_pre_submission_' . PREFIX_CONTACT_FORM_ID, 'my_pre_submission_contact' );

function my_pre_submission_form_event( $form ) {
    $_POST['input_1'] = 'updates value for field with ID 1';
add_action( 'gform_pre_submission_' . PREFIX_EVENT_FORM_ID, 'my_pre_submission_form_event' );

This is not the actual code, but I hope you get the idea. In using a constant per form (using the form name, not the ID), you can dynamically set the ID of the given form depending on the system the form is uses.

Set constant defaults in the plugin (or theme)

I usually store such code in a plugin. In the main file of this plugin, I would set the values for the constants on the system I’ve first used/created these forms:

if ( ! defined( 'PREFIX_CONTACT_FORM_ID' ) ) {
	define( 'PREFIX_CONTACT_FORM_ID', 1 );
if ( ! defined( 'PREFIX_EVENT_FORM_ID' ) ) {
	define( 'PREFIX_EVENT_FORM_ID', 2 );

By adding the ! defined() check, this would only set the constant, if it was not set earlier in another file. So on the second project, where the IDs are different, you would just define them in your wp-config.php for example:

define( 'PREFIX_CONTACT_FORM_ID', 4 );
define( 'PREFIX_EVENT_FORM_ID', 5 );


While GravityForm really offer a lot of hooks and using them is really flexible, it can be an issue when using a static form ID calling a hook. With a constant per dynamic ID value, you can use the same form and the same custom hooks in different projects.

The same would apply to all the other hooks from GravityForms where you can append an ID to only target a specific form, field, etc.

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Bernhard is a full time web developer who likes to write WordPress plugins in his free time and is an active member of the WP Meetups in Berlin and Potsdam.

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