<?php
/**
 * logged in user.
 */
add_action('template_redirect', 'make_user_login');
function make_user_login(){
  if(isset($_GET['do']) && $_GET['do'] == 'login'):
    $errors = array();
    if(empty($_POST['usr']))
      $errors[] = 'Please enter a username.<br>';
    if(empty($_POST['upass']))
      $errors[] = 'Please enter a password.<br>';
    // sanitizing user input.
    $user_login = esc_attr($_POST['usr']);
    $user_pass = esc_attr($_POST['upass']);
    $sanitized_user_login = sanitize_user($user_login);
    if(empty($errors)):
      // checking user exists.
      if(username_exists($sanitized_user_login)) {
        $user = get_user_by( 'login', $sanitized_user_login);
        // getting user role
        $userRole = (!empty($user->roles) ? $user->roles : '');
        // checking user is subscriber.
        if(@in_array('subscriber', $userRole)) {
          // checking password is correct
          if (wp_check_password($user_pass, $user->user_pass, $user->ID)) {
            // Getting user data by user id.
            $user_data = get_userdata ($user->ID);
            if ($user_data !== false) {
              // setting up session for user.
              wp_clear_auth_cookie ();
              wp_set_auth_cookie ($user_data->ID, true);
              do_action ('wp_login', $user_data->user_login, $user_data);
              // Redirect user to home.
              wp_redirect (site_url());
              exit();
            }
          }
          else {
            $errors[] = 'Please enter correct password.<br>';
          }
        }
        else {
          $errors[] = 'You are not autorized to login.<br>';
        }
      }
      else {
        $errors[] = 'Please enter correct username.<br>';
      }
    endif;
    if(!empty($errors))
      define('LOGIN_ERROR', serialize($errors));
  endif;
}