預設常數

以下常數由擴充功能定義，因此只有在擴充功能被編譯到 PHP 中，或者在執行時被動態載入後才有效。

SID (string)

Constant containing either the session name and session ID in the form of "name=ID" or empty string if session ID was set in an appropriate session cookie. This is the same id as the one returned by session_id().

PHP_SESSION_DISABLED (int)

Since PHP 5.4.0. Return value of session_status() if sessions are disabled.

PHP_SESSION_NONE (int)

Since PHP 5.4.0. Return value of session_status() if sessions are enabled, but no session exists.

PHP_SESSION_ACTIVE (int)

Since PHP 5.4.0. Return value of session_status() if sessions are enabled, and a session exists.