How to create file selection element in Zend Framework?

// creating object for Zend_Form_Element_File
$doc_file = new Zend_Form_Element_File('doc_file');

$doc_file->setLabel('Image')
     ->setMaxFileSize('512000')
     ->addValidator('Count', true, 1)
     ->addValidator('Size', true, 512000)
->setRequired(true)
     ->addValidator('Extension', true, 'jpg,jpeg,png,gif');

$doc_file->getValidator('Count')->setMessage('You can upload only one file');
$doc_file->getValidator('Size')->setMessage('Your file size cannot upload file size limit of 512 kb');
$doc_file->getValidator('Extension')->setMessage('Invalid file extension, only valid image with file format jpg, jpeg, png and gif are allowed.');