Login with username OR email

[Hitler]

Hello,
I'm not sure how I could go about allowing the user to login with their username or email. I'm think it would be something like this, but if it's wrong and you know how to fix it up, please tell me.

if(isset($_POST['login']))
        {
            $template->form->setData();
            unset($template->form->error);
         
            if($this->nameTaken($template->form->log_username))
            {
                if($this->isBanned($template->form->log_username) == false || $this->isBanned($_SERVER['REMOTE_ADDR']) == false)
                {
                    if($this->userValidation($template->form->log_username || $template->form->log_email, $core->hashed($template->form->log_password)))
                    {
                        $this->turnOn($template->form->log_username || $template->form->log_email);
                        $this->updateUser($_SESSION['user']['id'], 'ip_last', $_SERVER['REMOTE_ADDR']);
                        $template->form->unsetData();
                        header('Location: ' . $_CONFIG['hotel']['url'] . '/me');
                        exit;
                    }
                    else
                    {
                        $template->form->error = 'Details do not match';
                        return;
                    }
                }
                else
                {
                    $template->form->error = 'Sorry, it appears this user is banned<br />';
                    $template->form->error .= 'Reason: ' . $this->getReason($template->form->log_username);
                    return;
                }
            }
            else
            {
                $template->form->error = 'Username does not exist';
                return;
            }
        }
    }

And what would you need to edit for it to work in the form, it's currently this.

<form method="post" action="index">
Email:<br />
<input type="text" class="txt" style="width: 40%;" name="log_username" value="" /><br />
<br />
Password:<br />
<input type="password" class="txt" style="width: 40%;" name="log_password" value="" /><br />
<br />
<input type="submit" name="login" class="buttonize green" value="Login" />
</form>

Sorry if I'm off by a long shot, I'm not that familiar with PHP.
Thanks,
Hitler.