Laravel dynamic dropdown country and state

I'm trying to make two dropdown menus. These are the countries and states selections from my database. My problem is don't know how to make conditions that states must be dependent on countries. When I select [countryname] it will give a different selection of states name in my dropdown. So far here what I have done so far.

AdminController.php

public function user_register()
    {
        $countryname = DB::table('countries')
            ->get();
        $statename = DB::table('states')
            ->get();

        $title = ucwords(Lang::get('constants.user') . ' ' . Lang::get('constants.register')); 
        return View::make('register.user_register')
            ->with('title', $title)
            ->with('page', 'user_register')
            ->with('countryname', $countryname)
            ->with('statename', $statename)
    }

user_register.blade.php

<select class="form-control" id="countries" name="countries">
    <option value="">Please select</option>
        <?php foreach ($countryname as $key=>$countryname): ?>
        <option value="<?php echo $countryname->sortname; ?>"<?php
         if (isset($countries) && Input::old('countries') == $countryname->sortname) 
         {
             echo 'selected="selected"';
         }
         ?>>
         <?php  echo $countryname->sortname ." - ". $countryname->name  ; ?>
    </option>
    <?php endforeach; ?>
</select>


<select class="form-control" id="states" name="states">
    <option value="">Please select</option>
        <?php foreach ($statename as $key=>$statename): ?>
        <option value="<?php echo $countryname->name; ?>" <?php
        if (isset($states) && Input::old('states') == $statename->name)
        {
            echo 'selected="selected"';
        }
        ?>>
        <?php  echo $statename->name; ?></option>
        <?php endforeach; ?>
</select>

In my database

Table: countries

+-----------+--------------+------+-----+---------+----------------+
| Field     | Type         | Null | Key | Default | Extra          |
+-----------+--------------+------+-----+---------+----------------+
| country_id| int(11)      | NO   | PRI | NULL    | auto_increment |
| sortname  | varchar(3)   | NO   |     | NULL    |                |
| name      | varchar(150) | NO   |     | NULL    |                |
| phonecode | int(11)      | NO   |     | NULL    |                |
+-----------+--------------+------+-----+---------+----------------+

Table: states

+------------+------------------+------+-----+---------+----------------+
| Field      | Type             | Null | Key | Default | Extra          |
+------------+------------------+------+-----+---------+----------------+
| id         | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| name       | varchar(255)     | NO   |     | NULL    |                |
| country_id | int(11)          | NO   |     | NULL    |                |
+------------+------------------+------+-----+---------+----------------+