IFrames are not supported with XHTML 1.0 Strict Doctype.
When you use IFrame and your doctype is XHTML 1.0 Strict, then you cannot pass the W3C Markup Validation test. You always get errors.
The errors are like:-

Let the page path be: http://localhost/test/admin/index.php
Get the server name/site name of your website:
echo $_SERVER['SERVER_NAME'];

This article will provide you step by step guide to setup Google AdSense.

In this article, I will be illustrating about getting html source code of any website. I have done this in PHP.