Drupal 7 Form file uploads silently failing

Hi,

I tried the file uploads in my custom form using the "file" with required field option, but the system is throwing the "Required field error" even though I uploaded file.

I am using WAMPserver with PHP version 5.5+, so not a problem with the gpc_magic_quotes which should be set Off (but, this is deprecated in PHP 5.4).

Please see my code below:

function test_data_import_form($form, &$form_state) {
	$form = array();
	
	//$form['#attributes'] = array('enctype' => 'multipart/form-data');
	
	$form['import_data'] = array(
		'#type' => 'file',
		'#title' => t('Upload data file'),
		'#size' => 22,
		'#required' => TRUE,
	);
	
	$form['submit'] = array(
		'#type' => 'submit',
		'#value' => t('Submit'),
		'#validate' => array('test_data_import_validate'),
		'#submit' => array('test_data_import_submit'),
	);
	
	return $form;
}