ServiceSearchForm.php

<?php

namespace Drupal\uw_ct_service\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Url;

/**
 * Class ServiceSearchForm.
 *
 * Form for searching services.
 */
class ServiceSearchForm extends FormBase {

  /**
   * Returns a unique string identifying the form.
   *
   * The returned ID should be a unique string that can be a valid PHP function
   * name, since it's used in hook implementation names such as
   * hook_form_FORM_ID_alter().
   *
   * @return string
   *   The unique string identifying the form.
   */
  public function getFormId(): string {
    return 'service_search_form';
  }

  /**
   * Form constructor.
   *
   * @param array $form
   *   An associative array containing the structure of the form.
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The current state of the form.
   * @param bool $use_placeholder
   *   Flag to user placeholder.
   * @param string|null $placeholder
   *   The placeholder string.
   * @param string|null $description
   *   The description for the input element.
   * @param string|null $uuid
   *   The unique id.
   *
   * @return array
   *   The form structure.
   */
  public function buildForm(
    array $form,
    FormStateInterface $form_state,
    bool $use_placeholder = TRUE,
    string $placeholder = NULL,
    string $description = NULL,
    string $uuid = NULL
  ): array {

    // If there is no placeholder sent, then set it to
    // search all services.
    if ($use_placeholder && $placeholder == NULL) {
      $placeholder = 'Search within all services';
    }

    // If there is no uuid, generate it.
    if (!$uuid) {
      $uuid = uniqid();
    }

    // Add the unique id.
    $form['#attributes']['id'] = 'service-search-form-' . $uuid;