How to populate a dropdown from result_array

It would be better within Contacts_model a special method public function dropdown() { ... } to be created. In this special method it is not necessary all the fields to be retrieved, 'id' and 'names' are enough.

Code:

public function dropdown() {

    $result = $this->db
        ->select('id', 'names')
        ->get('departments')
        ->result_array();

    return array_columns($result, 'names', 'id');
}

And then the dropdown in the view will become:

Code:

echo form_dropdown(
            'department',
            array('' => '-- Choose --') + $departments /* as a result of $this->contacts_model->dropdown() */,
            '', // or set_value('department', $department)
            'id="department"'
        );