PHP如何结合AJAX删除数据？

$id = $_GET['id'];

/*删除数据逻辑*/

header('Content-Type:application/json');
json_decode([
	'code' => 1,
	'msg' => 'Delete success'
])

if (window.XMLHttpRequest)
{
    // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
    xmlhttp=new XMLHttpRequest();
}
else
{
    // IE6, IE5 浏览器执行代码
    xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
    if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
        alert(xmlhttp.responseText);
    }
}
xmlhttp.open("GET","del_data.php?id="+id,true);
xmlhttp.send();