forms - How Can I get autofocus on the first element (buildform) symfony -

in topictype class, used :

public function buildform(formbuilderinterface $builder, array $options) {     $builder             ->add('title', 'text')             ->add('content', 'ckeditor', array(                 'label' => 'contenu',                 'config_name' => 'my_custom_config',                 'config' => array('language' => 'fr'),))             ->add('save', 'submit')     ; } 

how can autofocus on first field "title", when display form?

$builder->add('title', 'text', array(     'attr' => array(         'autofocus' => true         )     );