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    gzencode

    (PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

    gzencode — Create a gzip compressed string

    Description

    function gzencode(string $data, int $level = -1, int $encoding = ZLIB_ENCODING_GZIP): string|false

    This function returns a compressed version of the input data compatible with the output of the gzip program.

    For more information on the GZIP file format, see the document: » GZIP file format specification version 4.3 (RFC 1952).

    Parameters

    data

    The data to encode.

    level

    The level of compression. Can be given as 0 for no compression up to 9 for maximum compression. If not given, the default compression level will be the default compression level of the zlib library.

    encoding

    The encoding mode. Can be FORCE_GZIP (the default) or FORCE_DEFLATE.

    FORCE_DEFLATE generates RFC 1950 compliant output, consisting of a zlib header, the deflated data, and an Adler checksum.

    Return Values

    The encoded string, or false if an error occurred.

    Examples

    The resulting data contains the appropriate headers and data structure to make a standard .gz file, e.g.:

    Example #1 Creating a gzip file

    <?php
$data = file_get_contents("bigfile.txt");
$gzdata = gzencode($data, 9);
file_put_contents("bigfile.txt.gz", $gzdata);
?>

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    User Contributed Notes 1 note

    up
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    jp dot amarok at email dot cz
    1 year ago
    It may be difficult to understand the differences between "gzcompress", "gzdeflate" and "gzencode". Here are my notes:

gzcompress()
------------
Uses ZLIB_ENCODING_DEFLATE (https://www.php.net/manual/en/zlib.constants.php#constant.zlib-encoding-deflate)
ZLIB compression algorithm as per RFC 1950.

Compatible with pigz. (Not compatible with gzip.)
Has a header (compression details, begins with 0x78) and a footer (Adler32 checksum of uncompressed data in big-endian).

gzdeflate()
------------
Uses ZLIB_ENCODING_RAW (https://www.php.net/manual/en/zlib.constants.php#constant.zlib-encoding-raw)
DEFLATE algorithm as per RFC 1951.

No header and footer. Pure DEFLATE.

gzencode()
------------
Uses ZLIB_ENCODING_GZIP (https://www.php.net/manual/en/zlib.constants.php#constant.zlib-encoding-gzip)
GZIP algorithm as per RFC 1952.

Compatible with gzip.
Header begins with magic number 0x1f8b, then compression method 8 (DEFLATE), no file flags, no timestamp, with operating system ID.
Footer contains CRC32 checksum of uncompressed data and then size of uncompressed data, both in little-endian.
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