预定义常量

以下常量由本扩展模块定义，因此只有在本扩展模块被编译到 PHP 中，或者在运行时被动态加载后才有效。

XATTR_ROOT (integer)

Set attribute in root (trusted) namespace. Requires root privileges.

XATTR_DONTFOLLOW (integer)

Do not follow the symbolic link but operate on symbolic link itself.

XATTR_CREATE (integer)

Function will fail if extended attribute already exists.

XATTR_REPLACE (integer)

Function will fail if extended attribute doesn't exist.