In facebook, we can specify a web page url and add comments to it, or fetch comments for it, with the Graph API.
Later we can fetch the comments for the page, using a sample code, and display them on my page, as a widget, using a javascript code.
Similarly, is it possible to setup comments for a web page virtually using google plus, and display them with a code, using the API ? I came across google plus client library for php, but not sure about how to achieve what i wanted, with it.
Currently there is no public write API for Google+ or a way to bi-directionally integrate Google+ comments with an outside web page.
You can incorporate comments from a Google+ post onto your static page. Here are a couple of resources that can illustrate how:
The full documentation for the Google+ read API is at https://developers.google.com/+/api/ and there are libraries for PHP and JavaScript at https://developers.google.com/+/downloads/
http://little418.com/2011/12/google-comments-on-your-static-html-blog.html contains some examples about how to echo comments from a Google+ post.