PHP:Select Data from the database and return json to client side

$id=$_REQUEST['id'];

$con= mssql_connect();

if (isset($id))
{

$Selectquery = " select x,y,z,CONVERT(char(10), mydate,110) as mydate,";

$Selectquery .="  from Mytable order by xyz desc";
$result=mssql_query($Selectquery);
if (!$myresult)
{
$themessage = 'Invalid query: ' . mysql_error() . "\n";
die($themessage);
}
$Xrows = array ();
while ($row = mssql_fetch_row($result))
{
$arr=array('field1'=>"".$row[0]."",'field2'=>"".$row[1]."",'field3'=>"".$row[2]."",
'field4'=>"".$row[3]."");
$Xrows[]=$arr;
}
$Arr[]=array( 'myArray'=>$Xrows);
mssql_close($con);
echo json_encode($Arr);