The pros and cons of using rel=”publisher” is a topic for another article. But let us see how to implement rel=”publisher” for your website. Most CMS and custom web applications will have one primary php file that control the display and logical flow of the entire website. Once you have identified the main php file, follow these steps:
1) Search for the closing </head> tag in the php file.
2) Visit your Google + page and notice the URL pattern in the browser. It would be something like:
https://plus.google.com/<unique Google Plus Id>/posts
You don’t need the posts part so remove it, and your url would be something like: https://plus.google.com/<unique Google Plus Id>
3) Open your main php file in a text editor and add the following lines before the closing </head> tag
<link href="https://plus.google.com/<your brand’s G+ id here (read step 2)>/" rel="publisher" />
<script type="text/javascript">
window.___gcfg = {lang: 'en'};
(function()
{var po = document.createElement("script"); po.type = "text/javascript"; po.async = true;po.src = "https://apis.google.com/js/plusone.js"; var s = document.getElementsByTagName("script")[0]; s.parentNode.insertBefore(po, s);
})();</script>
4) Verify the code by visiting http://www.google.com/webmasters/tools/richsnippets 
5) Enter your website url and if everything goes well, you will see a message under:
Extracted Author/Publisher for this page
publisher
linked Google+ page = https://plus.google.com/<your G+ Id>/
Verified: Publisher markup is verified for this page.
Google introduced rel=”author” and rel=”publisher” mark-ups to rank authors by reputation. It is speculated that, after 3-4 Google Algorithm updates, author and publisher rank will play a major role in ranking pages. Unfortunately, Google’s plan to spread the use of rel=”author” has been a failure with less than 5% users adopting it.