(PHP 7)
deflate_add — Incrementally deflate data
$context
   , string $data
   [, int $flush_mode = ZLIB_SYNC_FLUSH
  ] ) : stringIncrementally deflates data in the specified context.
contextA context created with deflate_init().
dataA chunk of data to compress.
flush_mode
      One of ZLIB_BLOCK,
      ZLIB_NO_FLUSH,
      ZLIB_PARTIAL_FLUSH,
      ZLIB_SYNC_FLUSH (default),
      ZLIB_FULL_FLUSH, ZLIB_FINISH.
      Normally you will want to set ZLIB_NO_FLUSH to
      maximize compression, and ZLIB_FINISH to terminate
      with the last chunk of data. See the » zlib manual for a
      detailed description of these constants.
     
   Returns a chunk of compressed data,  或者在失败时返回 FALSE.
  
   If invalid arguments are given, an error of level
   E_WARNING is generated.