php session trap

1. Two processes cannot open a session storage handle at the same time. For example, two processes cannot perform session_start() on a session id at the same time, otherwise there is a risk of deadlock.

2. Regardless of whether there is data in the session, calling session_start() will open a storage handle, such as opening a file or establishing a connection. So don’t callsession_start()unless necessary.

3. For the storage types of memcached and redis, there is no connection pool support between requests, that is, a new connection will be created for each request.

4. The generation of session id depends on the global variable$_SERVER['REMOTE_ADDR']and the current microseconds. If the server calling session_start() or session_id() is not directly facing users, you need to pay attention to whetherREMOTE_ADDRcorrect.

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