Gravity Forms Stripe Add-On V4.X | Not Compatible with PHP 8.X

Good Day!

It appears the Gravity Forms Stripe Add-On (latest version, V4.1) is not compatible with PHP 8.X

Specifically, when we switch from PHP 7.4.23 (our current set-up) to PHP 8.0.10, and click on our Gravity Forms button, “Schedule Appointment”, we get an infinite loop (spinning circle) next to the button and the form never processes. With PHP 7.4.23 we do not have this issue.

(Note: We’re also using the PayPal Checkout Add-On and it’s running great wth PHP 8.0.10)

Is anyone else experiencing (or has experienced) the same issue? We read Gravity Forms’ article on compatibility with PHP 8, but found nothing useful. In fact, the article does not mention anything about Gravity Forms Add-Ons. We also read this post but it did not help either.

If you’re a developer or coder, below please find our php_errorlog output. Might help identify the issue and fix it.

Help appreciated. If there are any additional helpful troubleshooting steps that we should perform, please let us know.

We’re slowly, but surely, starting to migrate our website(s) to PHP 8.X

Thank you!


[09-Sep-2021 15:54:19 UTC] PHP Fatal error: Uncaught TypeError: explode(): Argument #2 ($string) must be of type string, array given in /public_html/wp-content/plugins/gravityforms/common.php:3252

Stack trace:

#0 /public_html/wp-content/plugins/gravityforms/common.php(3252): explode('|', Array)

#1 /public_html/wp-content/plugins/gravityforms/forms_model.php(3480): GFCommon::get_selection_value(Array)

#2 /public_html/wp-content/plugins/gravityforms/forms_model.php(7731): GFFormsModel::is_value_match(Array, '', 'isnot', Object(GF_Appointment_Booking_Calendar), Array, Array)

#3 /public_html/wp-content/plugins/gravityforms/forms_model.php(3600): GFFormsModel::evaluate_conditional_logic(Array, Array, Array, NULL)

#4 /public_html/wp-content/plugins/gravityforms/forms_model.php(3371): GFFormsModel::get_field_display(Array, Object(GF_Field_PayPal), Array, NULL)

#5 /public_html/wp-content/plugins/gravityforms/forms_model.php(3201): GFFormsModel::is_field_hidden(Array, Object(GF_Field_PayPal), Array)

#6 /public_html/wp-content/plugins/gravityforms/forms_model.php(6649): GFFormsModel::create_lead(Array)

#7 /public_html/wp-content/plugins/gravityforms/form_display.php(293): GFFormsModel::get_current_lead()

#8 /public_html/wp-content/plugins/gravityforms/form_display.php(34): GFFormDisplay::maybe_add_review_page(Array)

#9 /public_html/wp-content/plugins/gravityforms/gravityforms.php(785): GFFormDisplay::process_form(16)

#10 /public_html/wp-includes/class-wp-hook.php(303): GFForms::maybe_process_form(Object(WP))

#11 /public_html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters(NULL, Array)

#12 /public_html/wp-includes/plugin.php(518): WP_Hook->do_action(Array)

#13 /public_html/wp-includes/class-wp.php(763): do_action_ref_array('wp', Array)

#14 / /public_html/wp-includes/functions.php(1291): WP->main('')

#15 /public_html/wp-blog-header.php(16): wp()

#16 /public_html/index.php(17): require('/home/customer/...')

#17 {main} thrown in /public_html/wp-content/plugins/gravityforms/common.php on line 3252

Hi Jonathan. I don’t see Stripe mentioned in the stack trace at all. It looks like this issue is related to the Appointment Booking Calendar?

GF_Appointment_Booking_Calendar is mentioned in the stack trace.

Have you tried using Stripe on the site with PHP 8.0+ and without the Appointment Booking Calendar plugin?

Hi Chris,

Good catch!

We will need to switch to a staging site to perform the test you recommended. Will advise shortly.

Also, we have contacted the developers of gAppointments (sent them the same info posted here). It appears they recognize their plugin is not yet compatible with PHP above 8.0.1. See below for their response.

Until we have a chance to test your recommendation with our staging site (to confirm indeed if the Stripe Add-On or gAppointments are the issue), please don’t close this topic.

If you or your developer(s) need to reach out to gAppointments, here’s their contact info:


Thank you!



This issue is added to our to-do list so that it will be resolved by the next update.


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