How about the SSO (Single Sign-on) solution for PHP?

Ask PHP SSO (Single Sign-on) solution???
Single Sign-on, such as www.aaa.com,www.bbb.com two sites, to achieve AAA login, BBB website also implement login
These two days on the Internet to view a lot of information
Basically say using the user Authentication Center, set ticket, I implemented the next, through the P3P cross-site to pass the cookie, but how to verify the legality of this cookie? PHP SSO Single Sign-on

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Set a token to a cookie at www.aaa.com login and verify the center to save this token
Token Access Verification Center when entering www.bbb.com, compared to saved tokens
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IFRAME cross-domain communication you can try it, it seems to be the solution now!

http://www.alloyteam.com/2012/08/lightweight-solution-for-an-iframe-cross-domain-communication/
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Haha, for the score.
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References:

token encryption set to a cookie, how is token encrypted? Is this encryption non-reversible? Just a comparison with the verification center?

You customize a private key to create tokens with the private key

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