PHP or RUBY webiste scraper/arhiver

Hello, This should be a very simple project for someone with the right skills. Summary of what it should do: It is a website scraper/ archiver that scrapes and checks a list of websites at regular intervals. It will need to visit a list of websites(up to 30) every 6 hours, if the website contains new content compared to last scrape, it will save a copy of the page both html and a image of the page. If it does not contain new content, it will revisit the page again in six hours. It will need to follow all links on that domain and save a copy of those pages. Example: if the home page contains links to a "contact" and "about" page it will need to visit and save those pages as well. What we do not need: We do not need a fancy admin interface or any login/user system. We will be importing the code into an existing login system. This project can be built in php or ruby, when bidding please list what platform you would be using. Any questions please ask. Thank you, Sean