This is a problem with a ordering search results on my website,
When a search is made, random results appear on the content page, this page includes pagination too.
I would have your PHP generate your random record numbers or rows to retrieve, pass those to your query, and save a cookie on the user's client indicating what records they've already seen.
There's no reason for that user specific data to live on the server (unless you're tracking it, but it's random anyway so who cares).