如何在使用Front Controller模式时在PHP项目中使用ob_start（）

How can I use ob_start() in my PHP project when I use Front Controller pattern? I mean I just want it for some files in my project not all files.

My index.php something like this and I want to use header(location:) redirect in register.php:

<?php
session_start();

require_once("../base/initialize.php");

switch($path)
{
    case '/':
    case '/index.php':
        require_once(MAIN_PATH.DS.'index.php');
        break;
    case '/user/register.php':
        require_once(M_USER_PATH.DS.'register.php');
        break;
    case '/user/login.php':
        require_once(M_USER_PATH.DS.'login.php');
        break;

I found my fault. I thought ob_start() must be the first thing in pages (like session_start()), but it's not necessary, you just put it before sending header.

So i put it before my header layout in register.php and redirection is done well.