预定义常量

下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。

System V message constants

Constant	Type	Changelog
MSG_IPC_NOWAIT	integer
MSG_EAGAIN	integer	As of 5.2.0
MSG_ENOMSG	integer	As of 5.2.0
MSG_NOERROR	integer
MSG_EXCEPT	integer