jQuery：在变更事件上将变量传递给php循环

I have to pass an array index to php loop onChange event

<select class='services' name="services" onChange="changeforservice(this.value);" >
  <option value="Treatment1 "  selected>Treatment1</option>
  <option value="Treatment2">Treatment2</option>
  <option value="Treamtment3">Treamtment3</option>
</select>

JavaScript to get srevices value :

 <script>
   function changeforservice(val){ }
 </script>

Now I have sub-services array against each service selected as below

$data  = array(  
  'Treatment1' => array(
    'option 1',
    'option 2',
  ), 

  'Treatment2' => array(
    'option 1',
    'option 2',
  ),        
);

on change event I want to pass data index as below

<?php foreach($data['selectedindex'] as $value):?>
  <?php  echo $value; ?>
<?php endforeach;?>

how do I pass the selected index value on change event.

Please help.