gzwrite

    (PHP 4, PHP 5, PHP 7, PHP 8)

    gzwrite — Binary-safe gz-file write

    Description

    gzwrite(resource $stream, string $data, ?int $length = null): int|false

    gzwrite() writes the contents of data to the given gz-file.

    Parameters

    stream

    The gz-file pointer. It must be valid, and must point to a file successfully opened by gzopen().

    data

    The string to write.

    length

    The number of uncompressed bytes to write. If supplied, writing will stop after length (uncompressed) bytes have been written or the end of data is reached, whichever comes first.

    Return Values

    Returns the number of (uncompressed) bytes written to the given gz-file stream, or false on failure.

    Changelog

    Version Description
    8.0.0 length is nullable now; previously, the default was 0.
    7.4.0 This functions returns false on failure now; previously 0 was returned.

    Examples

    Example #1 gzwrite() example

    <?php
    $string     = 'Some information to compress';
    $gz = gzopen('somefile.gz','w9');
    gzwrite($gz, $string);
    gzclose($gz);
    ?>

    See Also

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    User Contributed Notes 6 notes

    up
    2
    calmarius at nospam dot atw dot hu
    15 years ago
    gz compression is often used with tar archives. Building tar archives is quite easy. Here is a code snipplet which can be used for building tar archives before compressing them to tar.gz.

    <?php

    //\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
    // Adds file header to the tar file, it is used before adding file content.
    // f: file resource (provided by eg. fopen)
    // phisfn: path to file
    // archfn: path to file in archive, directory names must be followed by '/'
    //\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
    function TarAddHeader($f,$phisfn,$archfn)
    {
    $info=stat($phisfn);
    $ouid=sprintf("%6s ", decoct($info[4]));
    $ogid=sprintf("%6s ", decoct($info[5]));
    $omode=sprintf("%6s ", decoct(fileperms($phisfn)));
    $omtime=sprintf("%11s", decoct(filemtime($phisfn)));
    if (@    is_dir($phisfn))
    {
    $type="5";
    $osize=sprintf("%11s ", decoct(0));
    }
    else
    {
    $type='';
    $osize=sprintf("%11s ", decoct(filesize($phisfn)));
    clearstatcache();
    }
    $dmajor = '';
    $dminor = '';
    $gname = '';
    $linkname = '';
    $magic = '';
    $prefix = '';
    $uname = '';
    $version = '';
    $chunkbeforeCS=pack("a100a8a8a8a12A12",$archfn, $omode, $ouid, $ogid, $osize, $omtime);
    $chunkafterCS=pack("a1a100a6a2a32a32a8a8a155a12", $type, $linkname, $magic, $version, $uname, $gname, $dmajor, $dminor ,$prefix,'');

    $checksum = 0;
    for (    $i=0; $i<148; $i++) $checksum+=ord(substr($chunkbeforeCS,$i,1));
    for (    $i=148; $i<156; $i++) $checksum+=ord(' ');
    for (    $i=156, $j=0; $i<512; $i++, $j++) $checksum+=ord(substr($chunkafterCS,$j,1));

    fwrite($f,$chunkbeforeCS,148);
    $checksum=sprintf("%6s ",decoct($checksum));
    $bdchecksum=pack("a8", $checksum);
    fwrite($f,$bdchecksum,8);
    fwrite($f,$chunkafterCS,356);
    return     true;
    }
    //\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
    // Writes file content to the tar file must be called after a TarAddHeader
    // f:file resource provided by fopen
    // phisfn: path to file
    //\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
    function TarWriteContents($f,$phisfn)
    {
    if (@    is_dir($phisfn))
    {
    return;
    }
    else
    {
    $size=filesize($phisfn);
    $padding=$size % 512 ? 512-$size%512 : 0;
    $f2=fopen($phisfn,"rb");
    while (!    feof($f2)) fwrite($f,fread($f2,1024*1024));
    $pstr=sprintf("a%d",$padding);
    fwrite($f,pack($pstr,''));
    }
    }
    //\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
    // Adds 1024 byte footer at the end of the tar file
    // f: file resource
    //\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
    function TarAddFooter($f)
    {
    fwrite($f,pack('a1024',''));
    }

    ?>
    up
    2
    Kioob
    21 years ago
    This is a short example of use gzwrite function.
    <?php
    function gzcompressfile($source,$level=false){
    $dest=$source.'.gz';
    $mode='wb'.$level;
    $error=false;
    if(    $fp_out=gzopen($dest,$mode)){
    if(    $fp_in=fopen($source,'rb')){
    while(!    feof($fp_in))
    gzwrite($fp_out,fread($fp_in,1024*512));
    fclose($fp_in);
    }
    else     $error=true;
    gzclose($fp_out);
    }
    else     $error=true;
    if(    $error) return false;
    else return     $dest;
    }
    ?>

    the function gzcompressfile() compress a file 'data.csv' to 'data.csv.gz'. the function return false if error, and the new file name if it's ok.
    up
    1
    Anonymous
    16 years ago
    katzlbtjunk's method is certainly shorter, but it is unusable for anything except small files. It would try to load the whole file into memory, then create an entire compressed copy, and only then write it to disk. The other method given below will not exhaust memory like that.
    up
    0
    Take Heed
    13 years ago
    Read the description of gzwrite() very carefully. If the 'length' option is not specified, then the input data will have slashes stripped on systems where magic quotes are enabled. This is important information to know when compressing files.

    <?php
    $data     = fread($fp, 5000);
    gzwrite($fp2, $data, strlen($data));
    ?>

    Is the correct way to avoid issues with magic quotes.
    up
    -3
    repository at lamaresh dot net
    15 years ago
    This function add a line to a .gz compressed file

    <?php
    function AppendLineGz($file,$string) {
    if (    file_exists($file)) {
    $lines = gzfile($file);
    $lines[count($lines)] = "$string\r\n";
    $input=implode($lines);
    } else {    $input="$string\r\n";}
    $gz = gzopen($file,'w9');
    gzwrite($gz, $input);
    gzclose($gz);
    }
    ?>
    up
    -4
    katzlbtjunk at hotmail dot com
    16 years ago
    How about this instead:
    $s = file_get_contents('file.tar');
    file_put_contents('file.tar.gz',gzencode($s,9));
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