Queste costanti sono definite da questa estensione e sono disponibili solo se l'estensione è stata compilata nel PHP o se è stata caricata dinamicamente a runtime.
FORCE_GZIP
    (int)
   FORCE_DEFLATE
    (int)
   ZLIB_ENCODING_RAW
    (int)
   ZLIB_ENCODING_DEFLATE
    (int)
   ZLIB_ENCODING_GZIP
    (int)
   ZLIB_FILTERED
    (int)
   ZLIB_HUFFMAN_ONLY
    (int)
   ZLIB_FIXED
    (int)
   ZLIB_RLE
    (int)
   ZLIB_DEFAULT_STRATEGY
    (int)
   ZLIB_BLOCK
    (int)
   ZLIB_NO_FLUSH
    (int)
   ZLIB_PARTIAL_FLUSH
    (int)
   ZLIB_SYNC_FLUSH
    (int)
   ZLIB_FULL_FLUSH
    (int)
   ZLIB_FINISH
    (int)
   ZLIB_VERSION
    (string)
   zlib version number as a string.
    
   ZLIB_VERNUM
    (int)
   zlib version number as an int.
    
   ZLIB_OK
    (int)
   ZLIB_STREAM_END
    (int)
   ZLIB_NEED_DICT
    (int)
   ZLIB_ERRNO
    (int)
   ZLIB_STREAM_ERROR
    (int)
   ZLIB_DATA_ERROR
    (int)
   ZLIB_MEM_ERROR
    (int)
   ZLIB_BUF_ERROR
    (int)
   ZLIB_VERSION_ERROR
    (int)
   zlib library version is incompatible with the version assumed by the caller.
    
   