Request Detection

When to Use

You need to detect if a request is from HTMX and access request metadata (triggering element, target, prompt, etc.) in controllers or forms.

Using HtmxRequestInfoTrait

Forms automatically include this trait via FormBase. Controllers need to implement getRequest() method.

Reference: /core/lib/Drupal/Core/Htmx/HtmxRequestInfoTrait.php — 8 detection methods Reference: /core/lib/Drupal/Core/Form/FormBase.php line 48 — Trait inclusion

Available Methods

Method	Returns	Purpose
`isHtmxRequest()`	bool	TRUE if `HX-Request` header present
`isHtmxBoosted()`	bool	TRUE if `HX-Boosted` header present
`getHtmxCurrentUrl()`	string	Value of `HX-Current-URL` header
`isHtmxHistoryRestoration()`	bool	TRUE for history restore requests (cache miss)
`getHtmxPrompt()`	string	Value from prompt dialog if shown
`getHtmxTarget()`	string	Target element ID
`getHtmxTrigger()`	string	Triggering element ID
`getHtmxTriggerName()`	string	Triggering element name attribute

Pattern: Using in Forms

Forms automatically have access:

use Drupal\Core\Form\FormBase;

class MyForm extends FormBase {
  public function buildForm(array $form, FormStateInterface $form_state) {
    // Detect HTMX request
    if ($this->isHtmxRequest()) {
      // Get triggering element
      $trigger = $this->getHtmxTriggerName();

      if ($trigger === 'field_name') {
        // Handle specific field change
      }
    }

    return $form;
  }
}

Reference: /core/modules/config/src/Form/ConfigSingleExportForm.php lines 136-161 — Production example

Pattern: Using in Controllers

Controllers need to implement getRequest():

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Htmx\HtmxRequestInfoTrait;

class MyController extends ControllerBase {
  use HtmxRequestInfoTrait;

  protected function getRequest() {
    return \Drupal::request();
  }

  public function content() {
    if ($this->isHtmxRequest()) {
      // Return minimal HTMX response
    }
    return $full_page_build;
  }
}

Pattern: Detecting Triggering Element

HTMX automatically sends triggering element name via _triggering_element_name parameter:

// In form buildForm() method
$input = $form_state->getUserInput();
$trigger = $input['_triggering_element_name'] ?? '';

if ($trigger === 'config_type') {
  // Handle type selector change
} elseif ($trigger === 'config_name') {
  // Handle name selector change
}

Reference: /core/misc/htmx/htmx-assets.js lines 59-62 — JavaScript adds this parameter when HX-Trigger-Name header present

Common Mistakes

Using getHtmxTrigger() for form element names — Use getHtmxTriggerName() or getUserInput()['_triggering_element_name']
Not implementing getRequest() in controllers — Trait methods will fail
Assuming all requests are HTMX — Always check isHtmxRequest() before using other trait methods
Forgetting to handle non-HTMX fallback — Forms should work without JavaScript