php - How to convert stringified data to an object? -

my php has header('content-type: application/json') , json_encode.
ajax code use send data php file has datatype: 'json' , sending data string (json.stringify).
problem is, can't make $_post['data'] work on string.
way convert object?

edit: trying achieve is, sending data ajax php query looks information database , php file sends array using json ajax , ajax displays it.

ajax:

function op_prof(obj) {     var xval = obj.id;      $.ajax({     type: "post",     url: '../script/profile.php',     datatype: 'json',     data: json.stringify({'u_search':'xval'}),     cache: false,     success: function(data) {         console.log(data);         alert(data);         alert({u_search:xval}['u_search']);         $("#co_profile").html(data).show();     }   }); }; 

php:

<?php include(dirname(__file__). '/../script/config.php'); session_start(); $id = $_post['u_search']; foreach($pdo->query("select * users id='$id'") $row) {     $fullname = $row['fullname'];     $data = array("u_data"=> true,"inpt"=>"<p>my name " . $fullname . "</p>"); header('content-type: application/json'); echo json_encode($data); ?>  <?php $pdo = null; ?> 

i'd know other way of achieving (even without using json)

try json_decode("php://input");