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Add some general information about custom session save handlers relating to the session workflow.

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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@323385 c90b9560-bf6c-de11-be94-00142212c4b1
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Drak 2012-02-20 15:22:27 +00:00
parent c36d6e4eaf
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34
reference/session/examples.xml
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@ -243,6 +243,40 @@ here</a>.
will need to use <function>session_set_save_handler</function> to
create a set of user-level storage functions.
</para>
<para>
The callbacks specified in <function>session_set_save_handler</function> are methods
called by PHP during the life-cycle of a session: open, read, write and close and for
the houskeping tasks of deleting stored sessions and periodic garbage collection.
</para>
<para>
Therefor, PHP always requires session save handlers. The default is usually the
internal 'files' save handler, but can be overriden using
<function>session_set_save_handler</function> if you need anything other than PHP's
internal handlers. Alternative internal save handlers can also be provided by PHP extensions,
such as sqlite, memcache and memcached.
</para>
<para>
When the session starts, PHP will call the open() handler followed by the read() handler
which should return an encoded string extactly as it was originally passed for storage.
Once the read() handler returns the encoded string, PHP will decode it and then populate
the resulting array into the $_SESSION superglobal.
</para>
<para>
When PHP shuts down (or when <function>session_write_close</function> is called),
PHP will encode the $_SESSION superglobal into a specially serialized string and pass this
along with the session ID to the the write() callback.
After write() PHP will invoke the close() handler.
</para>
<para>
When a session is specifically destroyed, PHP will call the
destroy() handler with the session ID.
</para>
<para>
PHP will call gc() from time to time to expire any session
records according to the set max lifetime of a session. This routine
should delete all records from persistent storage which were last
accessed longer than the $lifetime.
</para>
</section>
</appendix>