post跨域第一种写法：
$.ajax({
    url:"http://ss01.xxx.cn/index.php/Admin/Book/add",
    crossDomain: true,
    dataType:'json',
    type:'POST',
    data:{username:55,tel:13912341234},
    // jsonp:'callback',
    success:function(data) {
        console.log(data,88);
    },
    timeout:3000
});
//php后端要加上：
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST');
header('Access-Control-Max-Age: 1000');
第二种写法：
$.ajax({
    url:"http://ss01.6-66.cn/index.php/Admin/Book/add",
    dataType:'jsonp',
    type:'POST',
    data:{username:55,tel:13912341234},
    jsonp:'callback',
    success:function(data) {
        console.log(data,88);
    },
    timeout:3000
});