gzencode

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

gzencode — Crea una stringa compressa con gzip

Descrizione

gzencode(string $data, int $level = -1, int $encoding_mode = FORCE_GZIP): string

Questa funzione restituisce una versione compressa di data compatibile con l'output del programma gzip.

Per ulteriori informazioni sul formato dei file GZIP, consultare il documento: » Specifica del formato di file GZIP versione 4.3 (RFC 1952).

Elenco dei parametri

data

I dati da codificare.

level

Il livello di compressione. Può essere dato come 0 per nessuna compressione fino a 9 per la massima compressione. Se non viene fornito, il livello di compressione predefinito adottato sarà quello di default della libreria zlib.

encoding_mode

La modalità di codifica. Può essere FORCE_GZIP (il default) o FORCE_DEFLATE.

Prima di PHP 5.4.0, se si utilizza FORCE_DEFLATE, si ottiene una stringa compressa col DEFLATE standard di zlib (comprendente gli header zlib) dopo un header del file gzip ma senza il checksum crc32 finale.

In PHP 5.4.0 e versioni successive, FORCE_DEFLATE genera un output conforme a RFC 1950, costituito da un header zlib, i dati compressi col DEFLATE e un checksum Adler.

Valori restituiti

La stringa codificata o false se si è verificato un errore.

Esempi

I dati risultanti contengono gli header e la struttura dati appropriati per creare un file .gz standard, ad esempio:

Example #1 Creare un file gzip

<?php
$data = implode("", file("bigfile.txt"));
$gzdata = gzencode($data, 9);
$fp = fopen("bigfile.txt.gz", "w");
fwrite($fp, $gzdata);
fclose($fp);
?>

Vedere anche:

gzdecode() - Decodes a gzip compressed string
gzdeflate() - Comprime una stringa
gzinflate() - Inflate a deflated string
gzuncompress() - Decomprime una stringa compressa
gzcompress() - Comprime una stringa
» Specifica del Formato dei Dati Compressi ZLIB (RFC 1950)

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User Contributed Notes 11 notes

down

Sam Dowling ¶

13 years ago


this is a benchmark test of gzencode (.txt file)
----------------------------------------------
original file size = 3.29 MB (3,459,978 bytes)
compress lvl 1 = 1.09 MB (1,144,006 bytes)
compress lvl 2 = 1.06 MB (1,119,518 bytes)
compress lvl 3 = 1.03 MB (1,085,567 bytes)
compress lvl 4 = 953 KB (976,538 bytes)
compress lvl 5 = 909 KB (931,486 bytes)
compress lvl 6 = 910 KB (932,516 bytes)
compress lvl 7 = 910 KB (932,608 bytes)
compress lvl 8 = 910 KB (932,646 bytes)
compress lvl 9 = 910 KB (932,652 bytes)
----------------------------------------------

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getmequick at dot com ¶

15 years ago


NOTE:

doing like this and so on

<?php
  file_put_contents('output.gz', gzencode( file_get_contents('input.file'),9));
?>

(complete file reading)

may cause memory overflow (Fatal error: Allowed memory size of ..), so it's better to read by parts/bytes.

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geompse at gmail dot com ¶

13 years ago


Had some trouble finding the correct way to send a Content-Length header with HTTP compression.
The pitch is to use gzencode (not gzdeflaten not gzcompress).

<?php

// disable ZLIB ouput compression
ini_set('zlib.output_compression','Off');

// compress data
$gzipoutput = gzencode($output,6);

// various headers, those with # are mandatory
header('Content-Type: application/x-download');
header('Content-Encoding: gzip'); #
header('Content-Length: '.strlen($gzipoutput)); #
header('Content-Disposition: attachment; filename="myfile.name"');
header('Cache-Control: no-cache, no-store, max-age=0, must-revalidate');
header('Pragma: no-cache');

// output data
echo $gzipoutput;

?>

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gazj at nukemodified dot com ¶

16 years ago


here is my clean up of supaplex %at% pcbkits %d0t% c0m
submission above.

function alt_gzdecode($gzdatadecode) {
  // seed with microseconds since last "whole" second.
  mt_srand((float)microtime()*1000000);
  $eh="/tmp/php-" . md5(mt_rand(0,mt_getrandmax())) . ".gz";
  if(file_exists($eh)){

  $gzf=fopen($eh,"w");
  fwrite($gzf,$gzdatadecode);
  fclose($gzf);

  $gzf = gzopen ($eh, "r");
  $gzdatadecode=gzpassthru($gzf);
  unlink($eh);

  return $gzdatadecode;
  }else{
  return 'File '.$eh.' was not found.';
  }
}

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tychay at alumni dot caltech dot edu ¶

22 years ago


The 10 byte string in gzencode is the standard gzip header. The first two bytes (1f 8b) define the return as a gzip file, the third byte (08) means that the body is compressed using the "deflate" algorithm. The rest is padding (00)'s.

Technically, I believe one should check if the third byte is hex 08 and if so strip off the first ten bytes and last four bytes and run inflate on it. The last four bytes are file size and checksum bits.

In practice, you can get away with just stripping the first 10 bytes and running inflate on it.

Hope this helps,

terry

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-1

pang dot lab at gmail dot com ¶

4 years ago


* Compressing file

function compressFile(string $filePath): ?string
{
    $compressedFile = $filePath.".gz";
    $data     = implode(",", file($filePath));
    $gzdata   = gzencode($data, 9);
    $fp       = fopen($compressedFile, "w");
    $successWrite = fwrite($fp, $gzdata);
    fclose($fp);
    if($successWrite === false) {
        return null;
    }

    return $compressedFile;
}

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-4

katzlbtjunk at hotmail dot com ¶

16 years ago


Aaron G. 07-Aug-2004 03:29 posted the excellent function gzdecode() (SEE BELOW)
BUGFIX: Change: if($flags & 1) to ... if($flags & 2)

Unfortunately the function gzencode() does NOT append a CRC! So the previous version worked with output of gzencode but not with output of the gzip program itself.

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-4

henryk at ploetzli dot ch ¶

22 years ago


Well, I was looking for a gzdecode too and didn't consider the temporary file example above to be very elegant. 
However, as is noted in the very first comment: gzencode() only adds a  10 byte header. 

I don't quite know what this header is supposed to be used for, but gzinflate() certainly doesn't like it, so I stripped it off:

function my_gzdecode($string) {
  $string = substr($string, 10);
  return gzinflate($string);
 }

That's useful to read HTTP-Connections that were compressed by mod_gzip.
-- 
Henryk Pl?tz
Gr??e aus Berlin

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-5

< supaplex %at% pcbkits %d0t% c0m > ¶

23 years ago


I was almost discouraged when I didn't find a gzdecode() function!  However, fear not, for I'll contribute my work... :)

function alt_gzdecode($str) {

  // seed with microseconds since last "whole" second.

  mt_srand((float)microtime()*1000000);

  $eh="/tmp/php-" . md5(mt_rand(0,mt_getrandmax())) . ".gz";





  $fd=fopen($eh,"w");

  fwrite($fd,$str);

  fclose($fd);



  $fd = gzopen ($eh, "r");

  $str=gzpassthru($fd);

  unlink($eh);



  return $str;

}



It's only ugly point is that it does not check to see if the file already exists.  You may also have to adjust reference names like $str and $fd if they stomp on your code. (Sorry, but this is all you get atm! ;} )  If your conserned about a race condition, cry for a internal gzdecode() function that actualy functions...

I spent about 3 hours straight debugging this problem.  I know the input data was valid, becuase I validated it with MD5() to compare to the md5's I had made of the input data before hand.  I'm not sure whats up with gzuncompress or gzinflate, but this works in its place . . .



Enjoy!

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-6

cbrunon at free dot fr ¶

18 years ago


Correct is:
<?php
  file_put_contents('output.gz', gzencode( file_get_contents('input.file'),9));
?>

down

-7

mm.. oops? - amendum (yes, tested hehe.) ¶

23 years ago


function alt_gzdecode($str) {

  // seed with microseconds since last "whole" second

  mt_srand((float)microtime()*1000000);

  $eh="/tmp/php-" . md5(mt_rand(0,mt_getrandmax())) . ".gz";



  $fd=fopen($eh,"w");

  fwrite($fd,$str);

  fclose($fd);



  unset($str);



  $fd = gzopen ($eh, "r");

  while (1==1) {

    $s=gzread($fd,10240);

    if ("$s" == "") {

      break;

    }

    $str=$str . $s;

  }

  unlink($eh);



  return $str;

}

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