AJAX: změna <select>u a zobrazení <select>u

<script>
function getXMLHTTP() { 
		var xmlhttp=false;	
		try{
			xmlhttp=new XMLHttpRequest();
		}
		catch(e)	{		
			try{			
				xmlhttp= new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch(e){
				try{
				xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
				}
				catch(e1){
					xmlhttp=false;
				}
			}
		}
		 	
		return xmlhttp;
	}
	
		
function getStates(strURL)
{		
	var req = getXMLHTTP();		
	if (req) 
	{
		
		req.onreadystatechange = function()
		{
			
			if (req.readyState == 4) 
			{			
				
				if (req.status == 200)
				{						
					document.getElementById('cur_code').value=req.responseText;						
				} 
				else 
				{
					alert("There was a problem while using XMLHTTP:\n" + req.statusText);
				}
			}				
		 }			
		 req.open("GET", strURL, true);
		 req.send(null);
	}			
}
</script>

<select name="country" onChange="getStates('find_states.php?country='+this.value)">
	<option value="">Select Country</option>
	<option value="usa">USA</option>
	<option value="uk">UK</option>
	<option value="cn">China</option>	
        </select>
        
        <select name="states id="">
          OPTIONY zde uz nevim
        </select>

<?php 

$country=$_REQUEST['country'];
switch($country)
{
	case "usa" :
                $zeme=array("nevim","texas");
		break;
	case "uk" :	
                $zeme=array("skotkos","anglie");
		break;
	case "cn" :	
                $zeme=array("cina1","cina2");
		break;
}
?>