javascript，ajax转PHP

I have this in my code and it doesnt work, please help me guys, I want to try passing the value when i pull from the dropdown, it process the data by onChange and showing the value in the tag

<label for="headmark" class="lbl-ui select">
    <select id="headmark" name="headmark" onChange="getVal(this)">                                
    <?php while (oci_fetch($headmark_parse)){?>                                                                                     
        <option value="<?php echo $head_mark ?>" id="headmark"> 
        <?php echo "$head_mark"; ?></option> 
        <?php } ?>
    </select>
</label>  

<script type="text/javascript">
       function getVal(val){
              $.ajax( {
              type: 'POST',
              url: update_fab_progress.php,
              data: "&val=" + val, 
              success: function(data) {
                        alert("data");
              }
          } );
       }
</script>
<?php
     echo $_POST['val'];
?>

Use chrome developer tool to help you debug. I think your parameter 'val' in javascript is a little strange. May be, you send a request with empty parameter.