I want someone to create a tool like [login to view URL] for me.
The user can insert a page and his email, and if that page changes, it alerts him through email. Inside this email you will provide a link to the tool, where a page will show what changed (something like a Wikipedia diff).
All users must login and can see all their "alerts", add, edit and delete them (as Google Alerts).
I want this developed in PHP language and using MySQL database.
Sir, here is solution scenario for your need. User need to register your site. User also need to register any pages to be monitored and being original pages. Your system will periodically performing test for changes and if change is detected an email notification will be sent. User can examine what the different is and provided option of actions. User can choose to restore from your site or accepted that change. If accepted change then the original page will be replaced with the new one.