This function returns a compressed version of the input
data using the ZLIB data
format, or FALSE if an error
is encountered. The optional parameter
level can be given as 0 for no compression up to
9 for maximum compression.
For details on the ZLIB compression algorithm see the
document "ZLIB Compressed Data Format Specification
version 3.3" (RFC 1950).
注: This is not the same as gzip compression, which includes some header data. See gzencode() for gzip compression.
See also gzdeflate(),
gzinflate(), gzuncompress(),
gzencode().