I have create an facebook apps that will send invitation when any one like the page page. But anyone have select and send invitation. But I am trying to build a automatic send invitation when anyone like the page. Please help me.
I don't think this is a good idea. There is one thing which will cause Facebook fans to "unlike" your Fan Page and that is spamming them with automated messages. You should be wary of using aggressive marketing tactics because they are counter productive in the long run. The best way to make your offers is by doing contests and other types of promotions.
You can send a request only if he is your friend... http://developers.facebook.com/docs/guides/canvas/#requests
Facebook already created this type of apps but if you create an apps when people like the pages then what you want in new?