var xmlhttp; 
 function  changeCity(str)
{ 
	
if (window.XMLHttpRequest)
  {
  // code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();

  }
else if (window.ActiveXObject)
  {
  // code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
 

  }
else
  {
  alert("Your browser does not support XMLHTTP!");
  }
  
		var url="city.php";
		url=url+"?q="+str;
	    xmlhttp.onreadystatechange=stateChanged; 
		xmlhttp.open("GET",url,false);
		xmlhttp.send(null);
		
}
function stateChanged() 
{ 
	if (xmlhttp.readyState==4)
	 { 
	 
		  document.getElementById("cities").innerHTML=xmlhttp.responseText;
	 } 
}