Somewhere I found out steganography .. the way of storing or hiding information within another information.. at times certain images are also used to hide the information.. Can i get an example or any thing further to know more about how this is implemented... or if at all is it possible to use this in php
You want the GD library in PHP to manipulate JPG images: http://php.net/manual/en/book.image.php
For an understanding of Steganography and Steganalysis, read this article: http://www.securityfocus.com/infocus/1684