问无法向同一页面发出ajax异步post请求

EN

<script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
<script>
    $( document ).ready(function() {
    //getting location of the user and assigning it to the variable
      $.get("http://ipinfo.io", function (response) {
        var usercity=response.city;
        console.log(usercity);
        $.ajax({
          //no need to provide url since we are making async call on the same page 
          type: "post",
          data: {cityinfo:usercity},
        });
      }, "jsonp");
    });
</script>

<?php
session_start(); 
$usercity=$_POST['cityinfo'];
echo $usercity; 
?>