function registration_form()
 {
     
    $html="
       <link href=' ".plugins_url()."/register/register-style.css' rel='stylesheet' type='text/css' />
     <div class='col-sm-12 register'>
     <form action='  ". $_SERVER['REQUEST_URI'] ."'  method='post'>
     <input type='text' name='username' id='user_name' placeholder='User Name'/><br>
     <input type='password' name='password' id='password' placeholder='Password '/><br>
     <input type='email' name='email' id='email' placeholder='Email Address'/><br>
     <input type='submit' value='Register' id='btn_register'/>
     </div>
     </form>
    ";
    return $html;
    
      print_r($_POST);
    $userdata=array(
     'user_login' =>  $_POST['username'],
     'user_pass' => $_POST['password'],
     'user_email' => $_POST['email']
    );
    $insert=wp_insert_user($userdata);
    //print_r($insert);
 }

  add_shortcode('register_ap','registration_form');