Android login fail when PHP MySQLi Change to PDO

Question

I successfully created an android login page using MySQLi. Now, I want to convert it from MySQLi to PDO. When I convert the config.php to PDO, the login page is unsuccessful. Below I want to show the code of successful login

config.php

    <?php
    define('HOST','localhost');
    define('USER','root');
    define('PASS','');
    define('DB','ot_worker');

    $conn = mysqli_connect(HOST,USER,PASS,DB) or die('Unable to Connect');
    ?>

login.php

<?php 

    require_once 'configPDO.php';

    //an array to display response
    $response = array();

        //for login we need the username and password 
        if(isTheseParametersAvailable(array('badgeid', 'pwd'))){
            //getting values 
            $badgeid = $_POST['badgeid'];
            $pwd = $_POST['pwd']; 

            //creating the query 
            $stmt = $conn->prepare("SELECT badgeid, email, fullname, roles_id, team_id FROM users WHERE badgeid = ? AND pwd = ? AND roles_id = 2");
            $stmt->bind_param("ss",$badgeid, $pwd);

            $stmt->execute();

            $stmt->store_result();

            //if the user exist with given credentials 
            if($stmt->num_rows > 0){

                $stmt->bind_result($badgeid, $email, $fullname, $roles_id, $team_id);
                $stmt->fetch();

                $user = array(
                    'badgeid'=>$badgeid, 
                    'email'=>$email,
                    'fullname'=>$fullname,
                    'roles_id'=>$roles_id,
                    'team_id'=>$team_id
                );

                $response['error'] = false; 
                $response['message'] = 'Login successfull'; 
                $response['user'] = $user; 
            }else{
                //if the user not found 
                $response['error'] = false; 
                $response['message'] = 'Invalid username or password';
            }
        }
    //displaying the response in json structure 
    echo json_encode($response);

    //function validating all the paramters are available
    //we will pass the required parameters to this function 
    function isTheseParametersAvailable($params){

        //traversing through all the parameters 
        foreach($params as $param){
            //if the paramter is not available
            if(!isset($_POST[$param])){
                //return false 
                return false; 
            }
        }
        //return true if every param is available 
        return true; 
    }

below is the code when I change config.php to PDO style

configPDO.php

<?php

$servername = 'localhost';
$username = 'root';
$password = '';
$dbname = 'ot_worker';

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $conn->exec("CREATE DATABASE IF NOT EXISTS `$dbname`");
    $conn->exec("use `$dbname`");

}
catch(PDOException $error) {
    $error->getMessage();
}
?>

Can anyone know what is the problem? is that at my configPDO.php?