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。
YAR_VERSION
(string)
YAR_CLIENT_PROTOCOL_HTTP
(integer)
YAR_CLIENT_OPT_PACKAGER
(integer)
YAR_CLIENT_OPT_TIMEOUT
(integer)
YAR_CLIENT_OPT_CONNECT_TIMEOUT
(integer)
YAR_PACKAGER_PHP
(string)
YAR_PACKAGER_JSON
(string)
YAR_ERR_OKEY
(integer)
YAR_ERR_OUTPUT
(integer)
YAR_ERR_TRANSPORT
(integer)
YAR_ERR_REQUEST
(integer)
YAR_ERR_PROTOCOL
(integer)
YAR_ERR_PACKAGER
(integer)
YAR_ERR_EXCEPTION
(integer)