通过发布jQuery发送JSON

I would like to implement an ajax call by sending data in JSON format . Something wrong in the syntax example :

var string_json='{"usr":{"name":"john","surname":"do"}}';
$.ajax({ url:"myurl",type:"post",data:{user:JSON.stringify(string_json)},
success:function(info){
        alert(info);                  }
           })

PHP side:

$var=$_POST['user'];
$user=json_decode($var);
echo $user->usr->name ;

at the end of the call http, I see nothing in the message alert.

string_json is already in JSON format, so you could do:

data: {user: string_json}

However, it's better to call JSON.stringify on the original object, rather than construct the JSON string by hand.

var user = { usr: { name: "john", surname: "do" } };
$.ajax({
    url: "myurl",
    type: "post",
    data: { user: JSON.stringify(user) }
    success: function(info) {
        alert(info);
    }
});

data needs to be a string, so call JSON.stringify on whatever you set data to.

var usr : { 
    name : "john", 
    surname : "do" 
  };
$.ajax({ url: "myurl", type:"post", data: JSON.stringify({ user: usr }),
success: function(info){
           alert(info);                  
         }
});