Get_option use inside switch select option


I try to make inside theme custom admin panel a switch select option. but i cannot get the value of switch case. following is my code:

$  bannerchange = $  _POST['bannerchange'];  if( get_option('bannerchange') != get_option($  bannerchange)) {             $  bannerchange = update_option( 'bannerchange', get_option($  bannerchange));  }  <?php if(isset($  _POST['wphw_submit']) && $  chk):?>   <div id="message" class="updated below-h2">     <p>Content updated successfully</p>   </div>     <?php endif;?>       <form method="post" action="">  <select name="wphw_submit" onchange="this.form.submit()">      <option value="page1"<?php if ($  bannerchange == "page1") { echo " selected"; } ?>>Custom Departure</option>      <option value="page2"<?php if ($  bannerchange  == "page2") { echo " selected"; } ?>>Fixed Departure</option> </select> <noscript><input type="submit" value="Submit"></noscript>  </div> <input type="submit" name="wphw_submit" value="Save changes" class="button-primary" /> <?php  switch ($  bannerchange) {     case 'page2': ?>                  <p>two</p>          <?php         break;     case 'page1':         ?>         <p>one</p>         <?php         break;     }     ?> 

$ bannerchange get always undefined.