在Ajax POST中正确拼写

I have two verions of code I believe should do the same thing, but the first one works and other one doesn't (Post vars: agenti, week_, team_). I have searched for few examples of how to do it the other way and I am sure my example is similar. What do I do wrong?

First:

$.post("index.html",
{
  agenti: getItems(),
  week_: week_array,
  team_: team
},
function(data,status){
  if (status = 'Success'){
    alert('Aktuální řazení operátorů bylo úspěšně uloženo.');
  } else {
    alert('Aktuální řazení operátorů se nepodařilo uložit.
Kontaktujte prosím správce aplikace.');
  }

Second:

$.ajax({
    type: "POST",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    url: "index.html",
    data: JSON.stringify({agenti: getItems(), week_: week_array, team_: team}),
    success: function (msg)
    {
        alert('Aktuální řazení operátorů bylo úspěšně uloženo.')
    },
    error: function (msg)
    {
        alert('Aktuální řazení operátorů se nepodařilo uložit.
Kontaktujte prosím správce aplikace.')
    } 
  });

I want to do the second one because I need to specify content type and i couldn't figure how to do it in the first way. Thanks you!

edit: I use IE; this code will be used only in IE.

so the first thing is that, no need to use JSON.stringify function, as the data accepts JSON objects, as well the string represented like a url (test1=1&test2=2...). So to use it like the following is ok.

data: {agenti: getItems(), week_: week_array, team_: team},

Also when you are using contentType: 'application/json' the GLOBAL $_POST variable is not being populated as it is being populated only for form-urlencoded data which is default value for contentType option, here you go with data from jQuery reference`

contentType (default: 'application/x-www-form-urlencoded; charset=UTF-8')

In order you like to use application/json, you can retrieve that information in PHP side using php input like this following. file_get_contents('php://input');

---Working Example---

Javascript:

$.ajax({
    type: "POST",
    // contentType: "application/json; charset=utf-8",
    dataType: "json",
    url: "http://localhost",
    data: {agenti: 'test1', week_: 'test2', team_: 'test3'},
    success: function(msg) {},
    error: function(msg) {}
});

PHP:

// Retrieve the input
var_dump(file_get_contents('php://input'));
// Use $_POST var
echo json_encode($_POST);