发布ajax请求，如何阅读？ [关闭]

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                    <p class="mb0 mt6">Closed <span title="2014-03-01 05:22:38Z" class="relativetime">6 years ago</span>.</p>
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i wanted to show you the "post" from my jquery.ajax:

enter image description here

because of:

   $.ajax({
    url: "checkAvailability.php",
      type: 'POST',
      dataType: "json",
      data: {username:data}, // this is important
    success: function(data) {
        if (data.result == 1) {
            $("#select-err").text(data.error);
        }
        else {
            $("#select-err").text(data.error);
        }
    }
});

now i wanted to ask you how to read such a post on an other page.. i am doing this:

if($availabilityChecker->check_availability($_POST['username'])) {

i thought its an array, but this doesnt work, any idea´s?? greetings!

</div>

from ajax side...

    id='123';
    editedroll= 'admin';
    var data = {'userid':id,'roll':editedroll}; 
    $.ajax({
        url : 'checkAvailability.php',
        data : {data:JSON.stringify(data)},
        type : 'POST',
        success : function(data)
        {
           alert(data);
        }
    })

in php side..

  if(isset($_POST['data']))
  {
      $data = $_POST['data'];
      $data = json_decode($data,true);
      echo $data['userid'] // will print **123**
      echo $data['roll'] // will print **Admin**
  }

hope it may help you