Untitled

use Drupal\Core\Database\Database;
use Drupal\Core\Form\FormStateInterface;

/**
 * Implements hook_form_alter().
 */
function yourmodule_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  // Check if the form is the one you want to alter.
  if ($form_id == 'your_form_id') {
    // Get the email ID from the form submission.
    $email = $form_state->getValue('email_field_name'); // Replace with the actual field name.

    // Perform a database query to retrieve groups associated with the email.
    $query = Database::getConnection()->select('group_content__invitee_mail', 'invitee')
      ->fields('invitee', ['entity_id'])
      ->condition('invitee.invitee_mail_value', $email);

    $entity_ids = $query->execute()->fetchCol();

    if (!empty($entity_ids)) {
      // Query for group information based on entity IDs.
      $group_query = Database::getConnection()->select('group_content_field_data', 'group_data')
        ->fields('group_data', ['gid'])
        ->condition('group_data.id', $entity_ids, 'IN');

      $group_ids = $group_query->execute()->fetchCol();

      if (!empty($group_ids)) {
        // Do something with the group IDs, for example, print them.
        foreach ($group_ids as $group_id) {
          drupal_set_message('Group ID: ' . $group_id);
        }
      }
      else {
        drupal_set_message('No groups found for the provided email.');
      }
    }
    else {
      drupal_set_message('Email not found in invitee mail table.');
    }
  }
}