Hello firend ,thanks for answer,

I have anoher question,

From:
http://www.w3schools.com/ajax/ajax_database.asp



The AJAX JavaScript
This is the JavaScript code stored in the file "selectcustomer.js":

var xmlHttp

function showCustomer(str)
{
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
{
alert ("Browser does not support HTTP Request")
return
}
var url="getcustomer.asp"
url=url+"?q="+str
url=url+"&sid="+Math.random()
xmlHttp.onreadystatechange=stateChanged
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
}

function stateChanged()
{
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText
}
}

function GetXmlHttpObject()
{
var objXMLHttp=null
if (window.XMLHttpRequest)
{
objXMLHttp=new XMLHttpRequest()
}
else if (window.ActiveXObject)
{
objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
}
return objXMLHttp
}




May you explain about this line?

url=url+"&sid="+Math.random()

Why does it create sid?
If we use PHP,Must I do that also?


Thanks in advance.