Form with two submission buttons

I try to create a form with two submit buttons and each button will use a different function: the default submitForm function and a custom submitFormEndSession function. So I have this code:

class EndSessionForm extends FormBase {

  /**
   * @var \Drupal
   */
  private $drupal;

  public function __construct() {
    $this->drupal = new Drupal();
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId(): string {
    return 'end_session_form';
  }

  public function buildForm(array $form, FormStateInterface $form_state): array {

    // ... some fields

    $form['submit'] = [
      '#type' => 'submit',
      '#value' => 'Close the session',
      '#name' => 'btnEnd',
    ];

    $form['stop'] = [
      '#type' => 'submit',
      '#value' => 'Stop the session',
      '#name' => 'btnStop',
    ];

    return $form;
  }

  public function submitForm(array &$form, FormStateInterface $form_state) {
    // Function to call with the btnEnd button
  }

  public function submitStopForm(array &$form, FormStateInterface $form_state) {
    // Function to call with the btnStop button
  }
}

According to the documentation of Drupal 9.2.x, the only thing I had to do is add a #submit parameter to the $form['stop'] element like this:

$form['stop'] = [
  '#type' => 'submit',
  '#value' => 'Stop the session',
  '#name' => 'btnStop',
  '#submit' => [ $this, 'submitStopForm' ] // link to the second submit function
]

But it doesn't work.

After many tries and researches, I've found a partial solution by adding this in buildForm:

$form['#submit'][] = [$this, 'submitStopForm'];

The two buttons are now linked to submitForm and submitStopForm, no matter if I put a #submit parameter on the buttons or not, submitStopForm is executed first then submitForm. But I'm wonder how I can link the first button to submitForm and the second one to submitStopForm properly and without enter in both functions when we click on one button.

Thanks and have a nice day!

I think you have to wrap the sumbit callback in another array, if you are using that callable notation. So either:

$form['stop'] = [
  '#type' => 'submit',
  '#value' => 'Stop the session',
  '#name' => 'btnStop',
  '#submit' => [ [$this, 'submitStopForm'] ] // Array of callables (which are arrays)
];

or this

$form['stop'] = [
  '#type' => 'submit',
  '#value' => 'Stop the session',
  '#name' => 'btnStop',
  '#submit' => [ 'submitStopForm' ] //Array of submit functions
]

You can also get the element that triggered the action from inside the submit function, but i tend to think the previous solution is better.

public function submitForm(array &$form, FormStateInterface $form_state) { 
    $submitButton = $form_state->getTriggeringElement(); 
    dump($sumbitButton); 
}

https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Form%21FormState.php/function/FormState%3A%3AgetTriggeringElement/8.2.x