title: Convert JSON made by PHP "json_encode", into array to plot those values with D3
body: <p>I know, there are so many question like this, but I still haven't understand how to plot my json with D3.</p>
  
  <p>Well, this is the PHP:</p>
  
  <pre><code>$sth = mysqli_query($con, "SELECT Time AS x, Value AS y FROM dati WHERE Data='2006-09-26' AND SensorType=6");
  $rows = array();
  while($r = mysqli_fetch_assoc($sth)) {
      $rows[] = $r;
  }
  echo json_encode($rows);
  </code></pre>
  
  <p>this give me a json that I can see by an js alert:</p>
  
  <pre><code>[{"x":"11:35:27","y":"500"},{"x":"11:40:40","y":"263"},{"x":"11:55:10","y":"440"},{"x":"12:11:34","y":"1063"},{"x":"12:16:48","y":"1065"},{"x":"12:22:01","y":"1121"}]
  </code></pre>
  
  <p>and the fallows is my "wrong" json that has requested the json and made the alert:</p>
  
  <pre><code>jQuery.ajax({
              url: "json.php",
              type: "POST",
              async: false,
              success: function (data) {
                  var obj = $.parseJSON(JSON.stringify(data));
                  alert(obj);
   }
  </code></pre>
  
  <p>Now, if i try to plot obj with d3 (or whatever I guess) it doesn't work,
  I think that's because obj is NOT in the right format.</p>
  
  <p>is there anyone so kind to help me?
  My goal is to plot those value in an LineChart</p>
  
  <p>Thanks!</p>