how to change the widget of view's exposed filter form?

Question

I have an exposed filter form, and its default widgets are textfields. I'd like to change them to selects based on values from database. I have tried hook_form_alter and hook_form_views_exposed_form_alter, but get an error:

An illegal choice has been detected. Please contact the site administrator.

The code I used to change the widget is like this and I've tried #validate option.

$form['field_address_province'] = array(
        '#type' => 'select',
        '#options' => $province_options,
        '#validate' => true,
        '#description' => 'Select address',
    );

Edit:

Sorry for the lack of infomation. The $province_options is an array like

Array
(
    [0] => Please Select
    [6] => Area1
    [7] => Area2
    [2] => Area3
)

Answer 1

i tested this kind of thing and found that when you try to switch a exposed widget field you need to provide an array with the empty first key, if it is checkboxes or radios; if new widget will be a select then you need to provide an array with the 'All' first key. E.g.:

//Suppose that you have a default input widget which you want to change to select widget.
//We will get the values which we want our new select widget will get as options:
$opts = array(
  'first_key' => 'First value',
  'sec_key' => 'Second value',
);

// Then we will add required 'All' first key:
$options = array('All' => 'Choose a value') + $opts;

// Then we will create our new select widget
$form['YOUR_FIELD_NAME'] = array(
     '#type' => 'select',
     '#title' => t('MY TITLE'),
     '#options' => $options,
   );