session_start — Initialize session data
session_destroy — Destroys all data registered to a session
session_name — Get and/or set the current session name
session_module_name — Get and/or set the current session module
session_save_path — Get and/or set the current session save path
session_id — Get and/or set the current session id
session_register — Register a variable with the current session
session_unregister — Unregister a variable from the current session
session_is_registered — Find out if a variable is registered in a session
session_decode — Decodes session data from a string
session_encode — Encodes the current session data as a string
Hello visitor, you have seen this page <? echo $count; ?> times.<p>
# the <?=SID?> is necessary to preserve the session id
# in the case that the user has disabled cookies
To continue, <A HREF="nextpage.php?<?=SID?>">click here</A>
session_register可以隐式地激发session_start（如果用户之前没发session_
start调用），当前的session注册了一个变量count，每次用户点击click here
的时候，这个变量都会增一。你可以自己试一下。<?=SID?>的意义不多赘述。
