Get contents of temporary uploaded file

Question

I've uploaded a file in a custom form and I can retrieve the file instance like this:

  $fid = $form_state->getValue('file')[0];
  $file = File::load($fid);

How can I get the contents of the file?

kint(file_get_contents($file->url()));

Returns false. If I visit the link manually, it gets downloaded.

Answer 1

You can't get the file from $form_state->getValue(). You have to upload the file first to the file table as temporary file with file_save_upload(). Then you can load the file content locally from $file->getFileUri().

  public function submitForm(array &$form, FormStateInterface $form_state) {

    $validators = ['file_validate_extensions' => ['txt']];
    if ($file = file_save_upload('file', $validators, FALSE, 0)) {
      $data = file_get_contents($file->getFileUri());
      drupal_set_message($data);
    }

  }