Call to a member function prepare() on null

1) My connection file (Connection.php)

class Connection
{
  function GetConnect()
  {
       $servername = "localhost";
       $dbname = "ladylike";
       $username = "root";
       $password = "";

       try
       {
            $conn = new PDO("mysql:host=$servername;dbname=$dbname", $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();
       }
  }
}


2) Login.php from where i am calling my common login function

<?php
include '../core/connection.php';
include "../core/base.php";

$objbase = new Base();
$ConnObj = new Connection();


 $action  = $_REQUEST['action'];
 $email  = $_REQUEST['email'];
 $password  = $_REQUEST['password'];

  switch($action)
  {
     case "checklogin":
     {
         CheckLogin($email,$password);
     }

  }
function CheckLogin($email,$password)
{
  global $objbase;
  global $ConnObj;
  $objbase->Login($email,$password);
}


3) And finally my common function file (base.php)

<?php
  require_once 'connection.php';

  $ConnObj = new Connection();
  $conn = $ConnObj->GetConnect();


class Base
{
    public $conn;
    public $pdo;

    function __construct()
    {
      $this->conn = new Connection;
      $this->pdo = $this->conn->GetConnect();
    }

   function Login($email,$password)
    {

       /*
            Here when i am using my connection fuile directly then it works

       $servername = "localhost";
       $dbname = "ladylike";
       $username = "root";
       $password = "";

       try
       {
            $conn = new PDO("mysql:host=$servername;dbname=$dbname", $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();
       }

        $stmt = $conn->prepare("SELECT UserSno,UserName,Email,`Password`,Mobile FROM `user` WHERE Active=1 AND UserName = ? AND `Password` = ?");
    $stmt->execute($email,$password);
        $stmt->execute();
        $stmt->fetch();




         */
         // But when i try to use object that time it gives me an error
    //Fatal error: Uncaught Error: Call to a member function prepare() on null in C:\wamp\www\ladylike\core\base.php on line 71
        //( ! ) Error: Call to a member function prepare() on null in C:\wamp\www\ladylike\core\base.php on line 71
        // line 71 mean below line (Yes i am not getting suggestion for prepare when i hit ctrl + space)

        $stmt = $this->pdo->prepare("SELECT UserSno,UserName,Email,`Password`,Mobile FROM `user` WHERE Active=1 AND UserName = ? AND `Password` = ?");
    $stmt->execute($email,$password);
        $stmt->execute();
        $stmt->fetch();
     }
}

?>