PHP: gzuncompress - Manual (original) (raw)

(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)

gzuncompress — Uncompress a compressed string

Description

Parameters

data

The data compressed by gzcompress().

max_length

The maximum length of data to decode.

Return Values

The original uncompressed data or [false](reserved.constants.php#constant.false) on error.

The function will return an error if the uncompressed data is more than 32768 times the length of the compressed input data or more than the optional parameter max_length.

Examples

Example #1 gzuncompress() example

<?php
$compressed   = gzcompress('Compress me', 9); <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>u</mi><mi>n</mi><mi>c</mi><mi>o</mi><mi>m</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>s</mi><mi>s</mi><mi>e</mi><mi>d</mi><mo>=</mo><mi>g</mi><mi>z</mi><mi>u</mi><mi>n</mi><mi>c</mi><mi>o</mi><mi>m</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>s</mi><mi>s</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">uncompressed = gzuncompress(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">u</span><span class="mord mathnormal">n</span><span class="mord mathnormal">co</span><span class="mord mathnormal">m</span><span class="mord mathnormal">p</span><span class="mord mathnormal">resse</span><span class="mord mathnormal">d</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal" style="margin-right:0.04398em;">z</span><span class="mord mathnormal">u</span><span class="mord mathnormal">n</span><span class="mord mathnormal">co</span><span class="mord mathnormal">m</span><span class="mord mathnormal">p</span><span class="mord mathnormal">ress</span><span class="mopen">(</span></span></span></span>compressed);
echo $uncompressed;
?>

Found A Problem?

heavyccasey at gmail dot com ¶

18 years ago

Note that gzuncompress() may not decompress some compressed strings and return a Data Error.

The problem could be that the outside compressed string has a CRC32 checksum at the end of the file instead of Adler-32, like PHP expects.

Workaround:
<?php
    function gzuncompress_crc32($data) {
         $f = tempnam('/tmp', 'gz_fix');
         file_put_contents($f, "\x1f\x8b\x08\x00\x00\x00\x00\x00" . $data);
         return file_get_contents('compress.zlib://' . $f);
    }
?>

anonymous at dekho-ji dot com ¶

13 years ago

To decode / uncompress the received HTTP POST data in PHP code, request data coming from Java / Android application via HTTP POST GZIP / DEFLATE compressed format

1) Data sent from Java Android app to PHP using DeflaterOutputStream java class and received in PHP as shown below
echo gzinflate( substr($HTTP_RAW_POST_DATA,2,-4) ) . PHP_EOL  . PHP_EOL;

2) Data sent from Java Android app to PHP using GZIPOutputStream java class and received in PHP code as shown below
echo gzinflate( substr($HTTP_RAW_POST_DATA,10,-8) ) . PHP_EOL  . PHP_EOL;

From Java Android side (API level 10+), data being sent in DEFLATE compressed format
        String body = "Lorem ipsum shizzle ma nizle";
        URL url = new URL("http://www.url.com/postthisdata.php");
        URLConnection conn = url.openConnection();
        conn.setDoOutput(true);
        conn.setRequestProperty("Content-encoding", "deflate");
        conn.setRequestProperty("Content-type", "application/octet-stream");
        DeflaterOutputStream dos = new DeflaterOutputStream(
                conn.getOutputStream());
        dos.write(body.getBytes());
        dos.flush();
        dos.close();
        BufferedReader in = new BufferedReader(new InputStreamReader(
                conn.getInputStream()));
        String decodedString = "";
        while ((decodedString = in.readLine()) != null) {
            Log.e("dump",decodedString);
        }
        in.close();

On PHP side (v 5.3.1), code for decompressing this DEFLATE data will be
    echo substr($HTTP_RAW_POST_DATA,2,-4);

From Java Android side (API level 10+), data being sent in GZIP compressed format

        String body1 = "Lorem ipsum shizzle ma nizle";
        URL url1 = new URL("http://www.url.com/postthisdata.php");
        URLConnection conn1 = url1.openConnection();
        conn1.setDoOutput(true);
        conn1.setRequestProperty("Content-encoding", "gzip");
        conn1.setRequestProperty("Content-type", "application/octet-stream");
        GZIPOutputStream dos1 = new GZIPOutputStream(conn1.getOutputStream());
        dos1.write(body1.getBytes());
        dos1.flush();
        dos1.close();
        BufferedReader in1 = new BufferedReader(new InputStreamReader(
                conn1.getInputStream()));
        String decodedString1 = "";
        while ((decodedString1 = in1.readLine()) != null) {
            Log.e("dump",decodedString1);
        }
        in1.close();

On PHP side (v 5.3.1), code for decompressing this GZIP data will be
    echo substr($HTTP_RAW_POST_DATA,10,-8);

Useful PHP code for printing out compressed data using all available formats.

$data = "Lorem ipsum shizzle ma nizle";
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
    echo chunk_split(strtoupper(bin2hex(gzcompress($data,$i))),2," ") . PHP_EOL  . PHP_EOL;
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
    echo chunk_split(strtoupper(bin2hex(gzdeflate($data,$i))),2," ") . PHP_EOL  . PHP_EOL;
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
    echo chunk_split(strtoupper(bin2hex(gzencode($data,$i,FORCE_GZIP))),2," ") . PHP_EOL  . PHP_EOL;
echo "\n\n\n";
for($i=-1;$i<=9;$i++)
    echo chunk_split(strtoupper(bin2hex(gzencode($data,$i,FORCE_DEFLATE))),2," ") . PHP_EOL  . PHP_EOL;
echo "\n\n\n";

Hope this helps. Please ThumbsUp if this saved you a lot of effort and time.

MagicalTux at php dot net ¶

15 years ago

Hi, I got an alternative for those zipped strings that gzuncompress() cannot extract.

It is a bit better than previous options as it do not create any temporary files, but it has to encode the string in base64, meaning it won't be as fast as a native equivalent (which is probably going to be gzdecode())

<?php
if (!function_exists('gzdecode')) {
    function gzdecode($string) { // no support for 2nd argument
        return file_get_contents('compress.zlib://data:who/cares;base64,'. base64_encode($string));
    }
}
?>

gabriel at bumpt dot n-et ¶

18 years ago

To uncompress in PHP a string that has been compressed using MySQL's COMPRESS() function, you need to discard the first four bytes of the binary data:

<?php

  /*
   * Example:
   *
   * insert into mytable (myfield, ...) values (COMPRESS('foobar'), ...)
   *
   * then:
   */
$compressed = //...select myfield from mytable where...
  /*
   * then:
   */ <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>u</mi><mi>n</mi><mi>c</mi><mi>o</mi><mi>m</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>s</mi><mi>s</mi><mi>e</mi><mi>d</mi><mo>=</mo><mi>g</mi><mi>z</mi><mi>u</mi><mi>n</mi><mi>c</mi><mi>o</mi><mi>m</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>s</mi><mi>s</mi><mo stretchy="false">(</mo><mi>s</mi><mi>u</mi><mi>b</mi><mi>s</mi><mi>t</mi><mi>r</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">uncompressed = gzuncompress(substr(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">u</span><span class="mord mathnormal">n</span><span class="mord mathnormal">co</span><span class="mord mathnormal">m</span><span class="mord mathnormal">p</span><span class="mord mathnormal">resse</span><span class="mord mathnormal">d</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal" style="margin-right:0.04398em;">z</span><span class="mord mathnormal">u</span><span class="mord mathnormal">n</span><span class="mord mathnormal">co</span><span class="mord mathnormal">m</span><span class="mord mathnormal">p</span><span class="mord mathnormal">ress</span><span class="mopen">(</span><span class="mord mathnormal">s</span><span class="mord mathnormal">u</span><span class="mord mathnormal">b</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mopen">(</span></span></span></span>compressed, 4));
?>

Of course, you can use MySQL's UNCOMPRESS() function.
I was just providing an alternate method.

squeegee ¶

16 years ago

One way to uncompress zlib-compressed data that is in a file without first reading in the file and then gzuncompressing it (maybe you have memory problems doing it that way) is to compile the zpipe.c program from zlib ( http://www.zlib.net/zpipe.c )...

on linux, etc:

# gcc -lz -o zpipe zpipe.c

# cp zpipe /usr/local/bin 

Then do this

<?php
 <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>u</mi><mi>n</mi><mi>c</mi><mi>o</mi><mi>m</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>s</mi><mi>s</mi><mi>e</mi><mi>d</mi><mo>=</mo><mi>s</mi><mi>h</mi><mi>e</mi><mi>l</mi><msub><mi>l</mi><mi>e</mi></msub><mi>x</mi><mi>e</mi><mi>c</mi><mo stretchy="false">(</mo><mi mathvariant="normal">&quot;</mi><mi>c</mi><mi>a</mi><mi>t</mi></mrow><annotation encoding="application/x-tex">uncompressed = shell_exec(&quot;cat </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">u</span><span class="mord mathnormal">n</span><span class="mord mathnormal">co</span><span class="mord mathnormal">m</span><span class="mord mathnormal">p</span><span class="mord mathnormal">resse</span><span class="mord mathnormal">d</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">s</span><span class="mord mathnormal">h</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord"><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:-0.0197em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">e</span></span></span></span><span class="vlist-s"></span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">x</span><span class="mord mathnormal">ec</span><span class="mopen">(</span><span class="mord">&quot;</span><span class="mord mathnormal">c</span><span class="mord mathnormal">a</span><span class="mord mathnormal">t</span></span></span></span>compressed_file | zpipe -d");

?>

emanuele at fondani dot it ¶

19 years ago

Note that the manual states that the input parameter must be a string compressed with gzcompress(), so it is not guaranteed that it will compress ANY zlib compressed string.
I realized this while decompressing some compressed string in a pdf file. The gzuncompress() function produces a data error, but the string can be successfully decompressed with other zlib decompressors.

More info here:
http://bugs.php.net/?id=39616

chappy at citromail dot hu ¶

20 years ago