Critical Error after submitting form, and when accessing notifications in admin UI [RESOLVED]

Hi, I just installed a site I’ve been developing and am encountering an critical error after submitting my Gravity Forms-powered contact form. The message is successfully writing to the database, and emails are being generated.

I also encounter the error when trying to go to any of the screen sunder Settings in the admin UI for the form (e.g. Settings > Notifcations).

WordPress and Gravity Forms are both fresh installs, and we’re running PHP 7.4. I’ve turned on the debugging log and am copying the output below, but not sure what to do. Also, I’ve deactivated all other plugins, and am using the latest version of the Divi theme.

Thanks in advance for any pro tips!

[15-Apr-2021 19:38:12 UTC] PHP Fatal error: Uncaught Error: Call to undefined function ctype_alnum() in /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-content/plugins/gravityforms/form_display.php:1572
Stack trace:
#0 /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-content/plugins/gravityforms/form_display.php(1538): GFFormDisplay::clean_up_files(Array)
#1 /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-content/plugins/gravityforms/form_display.php(153): GFFormDisplay::handle_submission(Array, Array, false)
#2 /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-content/plugins/gravityforms/gravityforms.php(634): GFFormDisplay::process_form(1)
#3 /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-includes/class-wp-hook.php(292): GFForms::maybe_process_form(Object(WP))
#4 /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-includes/class-wp-hook.php(316): WP_Hook->apply_filters(NULL, Array)
#5 /herm in /hermes/walnacweb05/walnacweb05ad/b588/moo.carriejmeyercom/restore061616/wp-content/plugins/gravityforms/form_display.php on line 1572

Resolved. I did some more googling and found:

“Check to make sure the ctype package is installed; It’s typically installed by default but some distros exclude it.”

I checked with my hosting support and found I had to activate the package via my php.ini file. So I added this line to the end of php.ini:

…and that resolved the issue. Hope this will be useful to someone else in the future!