validation process database connection and sql operation .

 <?php
$servername = "localhost";
$username = "root";
$password = "";

try {
    $conn = new PDO("mysql:host=$servername;dbname=login", $username, $password);
    // set the PDO error mode to exception
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
   // echo "Connected successfully";
    }
catch(PDOException $e)
    {
    echo "Connection failed: " . $e->getMessage();
    }
    ?>
    <?php
$username1=$_REQUEST['username'];
$useremail=$_REQUEST['useremail'];
$params=array($username1,$useremail);
$result=$conn->prepare("select * from userdata where user_name=? and user_email=?");
$result->execute($params);
$res=$result->fetchAll();
if($res)
{
    echo json_encode(array('success'=>true));
    //echo "valied user";
}
else
{
    echo json_encode(array('success'=>false));
    //echo "in valied user name and email";
}

?>