# 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。

`YAC_VERSION` (string)
`YAC_MAX_KEY_LEN` (int)
  Max length of a key could be, it is 48 bytes.
`YAC_MAX_VALUE_RAW_LEN` (int)
`YAC_MAX_RAW_COMPRESSED_LEN` (int)
`YAC_SERIALIZER_PHP` (int)
  Use php serialize as serializer
`YAC_SERIALIZER_JSON` (int)
  Use json as serializer(requrie --enable-json)
`YAC_SERIALIZER_IGBINARY` (int)
  Use igbinary as serializer(require --enable-igbinary)
`YAC_SERIALIZER_MSGPACK` (int)
  Use msgpack as serializer(require --enable-msgpack)
`YAC_SERIALIZER` (string)
  Which serialzier is yac used

`↑` and `↓` to navigate • `Enter` to select • `Esc` to close • `/` to open