What is best way to handle complex search?

I think it really depends on whether you need the search to be bookmarkable or shared. If you want it to be shareable then you'll have to use $_GET vars. To clean it up, though, you might consider some form of tokenization, either by creating a unique token and storing the params in the database for 30 days, or something, or maybe by serializing and base64 encoding the array? That might not give you exactly what you are looking for, but something like that should be able to work.

If not, then I would keep it clean and go with POST, but I wouldn't store it in the session. If it was their cart then I'd definitely consider the solution, but for a search it doesn't need to last so no sense taking up precious session space. Instead, I'd maintain the values throughout the search request. Then I'd put it in hidden form inputs one the page so it's available on every search.

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