Is there any way to prevent AJAX pages from being viewed alone in a browser?

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For example, when I want to update a part of my page with AJAX I would normally make the appropriate call to getPost.php which would return the markup to be inserted into my page. Is there any way to prevent a user from accessing this page directly (eg: example.com/getPost.php with the appropriate GET or POST arguments) and getting only part of the page since this should be used with AJAX as part of a whole, not alone?I don't think permissions can be set on the file since it's the client requesting the page but is there a way to do this by passing an extra argument that can serve as a check digit of sorts.