Form_alter with callback ajax for change/hidden existed field.

Hello,

I have the Views with the views_exposed_form, I have 2 dropdowns for filtering, For now I want to make a depends between the dropdown, for example: IF Dropdown 1 selected = 1, then hidden Dropdown 2 (field_xe_mau_tid2), otherwise show this.

Note that this two fields (dropdown) is already existed, I want to make visible then filter from the Views only.

unset($form['field_xe_mau_tid2']);
$form['field_xe_mau_tid']['#ajax'] = array(
		  // When 'event' occurs, Drupal will perform an ajax request in the
		  // background. Usually the default value is sufficient (eg. change for
		  // select elements), but valid values include any jQuery event,
		  // most notably 'mousedown', 'blur', and 'submit'.
		  //'event' => 'submit',
		  'callback' => 'field_xe_mau_callback',
		);

field_xe_mau_callback is callback function, but I tried dpm the variable but it's showing "Invalid form POST data" from the Log report.

Regards,
John