[PHP] Nuovo server, query non funzionano

$output = '';
  $result = $this->execute_query($query);
  $output .= '
  <table id="anagrafica" class="table table-bordered table-striped">
   <tr>
    <th >Data</th>
    <th width="10%">Categoria</th>
    <th width="30%">Cognome e Nome</th>
    <th width="30%">Data di Nascita</th>
    <th class="text-center" width="35%">Motivo</th>
    <th width="10%">Protocollo</th>
    <th width="35%">Assegnazione</th>
    <th width="10%">Aggiorna</th>
    <th width="10%">Precedenti</th>
   </tr>
  ';
  if(mysqli_num_rows($result) > 0)
  {
   while($row = mysqli_fetch_object($result))
   { $oDate = new DateTime($row->data);
$sDate = $oDate->format("d/m/Y");
    $output .= '
    <tr>
    <td>'.$sDate.'</td>
    <td align="center">'.$row->categoria.'</td>
    <td align="center">'.$row->cognome.'</td>
     <td align="center">'.$row->data_nascita.'</td>
     <td align="center">'.$row->motivo.'</td>
     <td align="center">'.$row->protocollo.'</td>
     <td align="center">'.$row->assegnazione.'</td>
     <td><button type="button" name="update" id="'.$row->id.'" class="btn btn-success btn-xs update">Aggiorna</button></td>
    <td align = center><a href=/archivio/fetch.php?id='.$row->id.'><img SRC=p.jpg ></a></td>
    </tr>
    ';
   }
  }

 if($_POST["action"] == "Fetch Single Data")
 {
  $output = '';
  $query = "SELECT * FROM registro WHERE id = '".$_POST["id"]."'";
  $result = $object->execute_query($query);
  while($row = mysqli_fetch_array($result))
  {

   $output["data"] = $row['data'];
   $output["categoria"] = $row['categoria'];
   $output["cognome"] = $row['cognome'];
   $output["data_nascita"] = $row['data_nascita'];
   $output["motivo"] = $row['motivo'];
   $output["protocollo"] = $row['protocollo'];
   $output["assegnazione"] = $row['assegnazione'];
     
  }
  echo json_encode($output);
 }