如何在php中追溯链接包含多个头文件

This is what I'm trying to figure out.

In other words if I write the following at the very beginning of index.php:

<?php include("header.php"); ?>

That works. ...but, if I go one step further and ALSO write the following at the beginning of header.php:

<?php include("html_header.php"); ?>

What happens then is the application only renders up to header.php. Why does it not render html_header.php?

Hope this is clear enough for future references. I would also like to know if there is anyway of achieving this type of chaining especially when relating to the headers. Thank you.

Wow! I feel like such an idiot. First of all, I was missing a quotation mark(?). In header.php I had <php require("html_header.php") ?> which is why it wasn't working but even if that hadn't worked, all I really needed to do was place both the include of header.php and the require of html_header.php together in index.php instead of separate on each file. Why I tried to do it the other way, I have no idea, but this was a real brain fart. Thanks anyways @David Kuna.