PHP Features Session Mechanism 2—Session and its use

Session mechanism (Session) is used in PHP to save some data in concurrent access. This can help create a more user-friendly program and increase the appeal of the site.
A visitor to your web site will be assigned a unique id, which is the so-called session id. This id can be stored in a cookie on the user side or passed through the URL.
Session support allows you Store the data from the request in the superglobal array $_SESSION. When a visitor visits your site, PHP will check automatically (if session.auto_start is set to 1) or at your request (explicitly via session_start() or Implicitly passed by session_register()) if the current session id was created by a previously sent request. If this is the case, then the previously saved environment will be rebuilt.
$_SESSION (and all registered variables) will be used by PHP The built-in serialization method performs serialization when the request is completed. The serialization method can be set to a specified method through the session.serialize_handler PHP configuration option. Registered variables that are not defined will be marked as undefined. During concurrent access, These variables are not defined by the session module unless the user later defines them. Because session data is serialized, resource variables cannot be stored in the session. Serialization handles (php and php_binary) are subject to register_globals restrictions. Furthermore, special characters (| and !) contained in numeric or string indexes cannot be used. Using these characters will result in an error when closing script execution. php_serialize has no such restriction. php_serialize is available from PHP 5.5.4 onwards.
Example 1, simple use of session:

session_cache_expire — Return current cache expire
session_cache_limiter — Get and/or set the current cache limiter
session_commit — session_write_close 的别名
session_decode — Decodes session data from a session encoded string
session_destroy — Destroys all data registered to a session
session_encode — 将当前会话数据编码为一个字符串
session_get_cookie_params — Get the session cookie parameters
session_id — Get and/or set the current session id
session_is_registered — 检查变量是否在会话中已经注册
session_module_name — Get and/or set the current session module
session_name — Get and/or set the current session name
session_regenerate_id — Update the current session id with a newly generated one
session_register_shutdown — Session shutdown function
session_register — Register one or more global variables with the current session
session_save_path — Get and/or set the current session save path
session_set_cookie_params — Set the session cookie parameters
session_set_save_handler — Sets user-level session storage functions
session_start — Start new or resume existing session
session_status — Returns the current session status
session_unregister — Unregister a global variable from the current session
session_unset — Free all session variables
session_write_close — Write session data and end session