Try this
Code:
xmlhttp.open("GET","http://www.website.com/here.php?q="+encodeURIComponent(str)+"&r="+encodeURIComponent(str2)+"&s="+encodeURIComponent(str3)+"&t="+encodeURIComponent(str4),true);
And take care to the warning on
this page (there is no need to decode).