(PHP 5 >= 5.4.0, PHP 7)
SessionHandlerInterface::gc — Cleanup old sessions
$maxlifetime
) : intCleans up expired sessions. Called by session_start(), based on session.gc_divisor, session.gc_probability and session.gc_maxlifetime settings.
maxlifetime
Sessions that have not updated for the last maxlifetime seconds will be removed.
会话存储的返回值（通常成功返回 0，失败返回 1）。