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I n开发者_运维百科eed to be able to detect if a used already visited a particular page.

I can set a cookies at their initial visit. I can also store some environment, such as IP, browser, OS, perhaps even language and create some string, like MD5 to compare against current visitor's environment.

Is there another method I should consider?

I work with PHP.

This isn't well defined enough for me to understand why just using cookies wouldn't satisfy this problem. A cookie has a domain and path that you can set on the server for each page they visit. As they visit each page you can look at those two settings to figure out if they have the cookie set on their browser or not and hence they have visited the page. You really don't have to get anymore sophisticated than that if all you want to know is did they visit the page before now.