PHP distributed and massive data processing related issues

PHP distributed and massive data processing issues
Now my company needs to do a micro-BO system, the user volume is large, the requirement to support millions of users at the same time online, they say is the use of what caching technology good, some people suggest to write in C + + background, some suggest using memcache do cache, because we this system has a im,im need to interact with the site, c+ + Write background is sure to, but this cache is used Memcache or C + + implementation of it.

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Memcache is originally written in C + +, and a C + + redo a difference.
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What language is not the key, the key is to build a multi-layered "storage layer", like the CPU, there is a cache, level two cache, level three cache, you need to fully consider the data stored in disk, DB, MEM, reasonably organized.

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