如何通过ajax和php传递日期

JAVASCRIPT

pokazSeanse(x){
[...]
x = "2013-04-25";
xmlhttp.open("GET","main/seanse.php?termin="+x,true);
xmlhttp.send();
}

seanse.php

$termin = $_GET['termin'];
echo $termin;

It shows "20132013". I need to get the full date