About passing value in php page

<script type="text/javascript">   
function getsel(){  
    var obj = document.getElementById("sel").value;  
    if(obj== ""){  
        obj = "0";  
    }  
    var newhref = "b.php?obj="+obj;  
    var ona = document.getElementById(&#39;ona&#39;);  
    ona.href = newhref;  
}  
  
</script>  
<select id="sel">  
      <?php foreach ($sql_res as $value) { ?>  
<option value="<?php echo $value[belongs];?>"><?php echo $value[belongs];?></option>  
 <?php };?>  
</select>

<?php  
$obj = $_REQUEST[&#39;obj&#39;];  
echo $obj;  
?>