ajax_form_callback in core/includes/ajax.inc

Page callback: Handles Ajax requests for the #ajax Form API property.

backdrop_build_form in core/includes/form.inc

Builds and processes a form for a given form ID.

backdrop_form_submit in core/includes/form.inc

Retrieves, populates, and processes a form.

drupal_process_form in core/includes/drupal.inc

Processes a form submission.

FieldAttachOtherTestCase::testFieldAttachSubmit in core/modules/field/tests/field.test

Test field_attach_submit().

file_ajax_upload in core/modules/file/file.module

Ajax callback: Processes file uploads and deletions.

FormsElementsTableSelectFunctionalTest::formSubmitHelper in core/modules/simpletest/tests/form.test

Helper function for the option check test to submit a form while collecting errors.

FormsTestCase::testRequiredFields in core/modules/simpletest/tests/form.test

Check several empty values for required forms elements.