How to ignore pageviews by search engines on a PHP page?

I have a particular PHP 开发者_C百科page that I want to conditionally do things only if the visitor is not a search engine. Are there some good regex to match $_SERVER['HTTP_USER_AGENT']?

Or would it be better to do a javascript redirect back to the page but set a flag, since search engines don't have javascript? (I don't have to worry much about my users not having Javascript for this page.)

I don't want to completely exclude search engines from hitting the page though, so save the robots.txt suggestion.

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You have to use a browser detection script with an up to date user agent database.

Here is one.