ajax simple

function ajax(){ var ajaxrequest; ajaxrequest=new XMLHttpRequest();
  ajaxrequest.onreadystatechange=function()
{ if(ajaxrequest.readyState==4)
{ document.myform.kq.value=ajaxrequest.responseText; } }
  var so1=document.getElementById('so1').value; 
var so2=document.getElementById('so2').value;   
ajaxrequest.open("Get","ketqua.php?so1="+so1+"&so2="+so2,true); 
ajaxrequest.send(null); } 
</script>   <form  name="myform">  
<input type="text" id="so1"  />
 <input type="text" id="so2"  /> 
<input type="text" id="kq"  />  
<input type="button" value="ok" onclick="ajax()" />   </form>