i can't upload file in symfony2 without form class

Question

I create a form manually, I can retrieve the name of my file at my controller but I can't upload the file here is my form

<form action="{{ path('innova_forum_multimodal_add_contribution_file', {id: id }) }}" method="post">

          Choisissez le fichier à deposer : 
          <input type="file" id="file" name="file" required="required"/>
          <input type="reset" value="Annuler" class="btn btn-primary" />
          <input type="submit" value="Valider" class="btn btn-primary"/>
</form>

here is my controller

$request = $this->getRequest();
    if($request->getMethod() == 'POST')
    {
      $dir = $this->get('kernel')->getRootDir().'/../web/uploads/files/';
      $name = "fichier";
      foreach($request->files as $uploadedFile) {
        $file = $uploadedFile->move($dir, $name);
    }

I can't use the form with Form builder because I already have 3 forms in the same page thank you in advance

here is the result of

$file = $request->files->get('upload');
var_dump($file); // => NULL

var_dump($request->request->all());
/* OUTPUT
array(1) { ["file"]=> string(7) "php.ini" }
*/
var_dump($request->files);
// OUTPUT
//object(Symfony\Component\HttpFoundation\FileBag)#11 (1) 
//      { ["parameters":protected]=> array(0) { } }

Answer 1

在表单中设置加密类型

<form enctype="multipart/form-data" action="{{ path('innova_forum_multimodal_add_contribution_file', {id: id }) }}" method="post">