gzinflate

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

gzinflate — Inflate a deflated string

Description

gzinflate(string $data, int $max_length = 0): string|false

This function inflates a deflated string.

Parameters

data: The data compressed by gzdeflate().
max_length: The maximum length of decoded data.

Return Values

The original uncompressed data or 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, unless max_length is 0, more than the optional parameter max_length.

Examples

Example #1 gzinflate() example

<?php
$compressed   = gzdeflate('Compress me', 9);
$uncompressed = gzinflate($compressed);
echo $uncompressed;
?>

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User Contributed Notes 10 notes

down

anonymous at dekho-ji dot com ¶

12 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 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.

down

felix dot klee at inka dot de ¶

12 years ago

The code below illustrates usage of the second parameter, in particular to protect against fatal out-of-memory errors. It outputs:



1000000

error



Tested with PHP 5.3 on 32bit Linux.



<?php



function tryToGzinflate($deflatedData, $maxLen = 0) {

  $data = gzinflate($deflatedData, $maxLen);

  if ($data === false)

    echo 'error<br>';

  else

    echo strlen($data).'<br>';

}



/ random data:

$data = '';

for ($i = 0; $i < 1000000; $i++)

  $data .= chr(mt_rand(97, 122)); / a-z



$deflatedData = gzdeflate($data);



ini_set('memory_limit', '5M'); / plenty of memory

tryToGzinflate($deflatedData);

tryToGzinflate($deflatedData, strlen($data));



ini_set('memory_limit', '100'); / little memory

tryToGzinflate($deflatedData, 100);

tryToGzinflate($deflatedData); / causes fatal out-of-memory error

?>

down

vitall at ua dot fm ¶

15 years ago

The correct function for gzip and chunked data particularly when you get "Content-Encoding: gzip" and "Transfer-Encoding: chunked" headers:



<?php

function decode_gzip($h,$d,$rn="\r\n"){

if (isset($h['Transfer-Encoding'])){

 $lrn = strlen($rn);

 $str = '';

 $ofs=0;

 do{

    $p = strpos($d,$rn,$ofs);

    $len = hexdec(substr($d,$ofs,$p-$ofs));

    $str .= substr($d,$p+$lrn,$len);

     $ofs = $p+$lrn*2+$len;

 }while ($d[$ofs]!=='0');

 $d=$str;

}

if (isset($h['Content-Encoding'])) $d = gzinflate(substr($d,10));

return $d;

}

?>



Enjoy!

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Steven Lustig ¶

14 years ago

You can use this to uncompress a string from Linux command line gzip by stripping the first 10 bytes:



<?php

$inflatedOutput = gzinflate(substr($output, 10, -8));

?>

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boris at gamate dot com ¶

21 years ago

When retrieving mod_gzip'ed content and using gzinflate() to decode the data, be sure to strip the first 10 chars from the retrieved content.



<?php $dec = gzinflate(substr($enc,10)); ?>

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patatraboum at free dot fr ¶

17 years ago

Some gz string strip header and return inflated

It actualy processes some first member of the gz

See rfc1952 at http://www.faqs.org/rfcs/rfc1952.html for more details and improvment as gzdecode



<?php

function gzBody($gzData){

    if(substr($gzData,0,3)=="\x1f\x8b\x08"){

        $i=10;

        $flg=ord(substr($gzData,3,1));

        if($flg>0){

            if($flg&4){

                list($xlen)=unpack('v',substr($gzData,$i,2));

                $i=$i+2+$xlen;

            }

            if($flg&8) $i=strpos($gzData,"\0",$i)+1;

            if($flg&16) $i=strpos($gzData,"\0",$i)+1;

            if($flg&2) $i=$i+2;

        }

        return gzinflate(substr($gzData,$i,-8));

    }

    else return false;

}

?>

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spikeles_ at hotmail dot com ¶

18 years ago

This can be used to inflate streams compressed by the Java class java.util.zip.Deflater but you must strip the first 2 bytes off it. ( much like the above comment )



<?php $result = gzinflate(substr($compressedData, 2)); ?>

down

niblett at gmail dot com ¶

13 years ago

alternative, with detection for optional filename header
<?php
function gzdecode($data) {

        / check if filename field is set in FLG, is 4th byte
        $hex = bin2hex($data);

        $flg = (int)hexdec(substr($hex, 6, 2));

        / remove headers
        $hex = substr($hex, 20);

        $ret = '';
        if (  ($flg & 0x8) == 8 ){
                print "ello";
                for ( $i = 0; $i < strlen($hex); $i += 2 ){
                        $value = substr($hex, $i, 2);
                        if ( $value == '00' ){
                                $ret = substr($hex, ($i+2));
                                break;
                        }
                }
        }
        return gzinflate(pack('H*', $ret));
}
?>

down

akniep at rayo dot info ¶

12 years ago

Take care when using the optional second parameter $length!

In our tests -at least in certain situations- we were unable to determine the actual use of this parameter, plus, it lead to the script either being unable to inflate compressed data or crash due to memory-problems.



Example:

When trying to inflate the compressed data from a website, we were literally unable to find a value (other than 0) for $length in order to make gzinflate work... while without the second parameter (or setting it to 0) gzinflate worked like a charm:



<?php

/ -----------------------------------------------------------------------

/ Test 1 works without problems. Memory peak usage: Before inflating: 24.787 kB; after: 24.844 kB.

gzinflate( substr($deflated_body, 10) );



/ -----------------------------------------------------------------------

/ ALL three of the following tests failed with a warning. Memory peak usage: Before inflating: 24.787 kB; after: 298.262 kB.

gzinflate( substr($deflated_body, 10),       200 * strlen($deflated_body) );

gzinflate( substr($deflated_body, 10),     32768 * strlen($deflated_body) );

gzinflate( substr($deflated_body, 10),     11000 );

gzinflate( substr($deflated_body, 10), 280000000 );    / the PHP memory limit was set to 300MB  (memory_limit=300M)

=>

Warning:  gzinflate() [function.gzinflate]: insufficient memory in [...]



/ -----------------------------------------------------------------------

/ The last test failed with a fatal error. Memory peak usage: Before inflating: 24.787 kB; after: ? (> 300M).

gzinflate( substr($deflated_body, 10), 300000000 );    / the PHP memory limit was set to 300MB  (memory_limit=300M)

=>

Fatal error:  Allowed memory size of 314572800 bytes exhausted (tried to allocate 300000000 bytes) in 

?>



In short: We were unable to determine the actual use of the second parameter in certain situations.

Be careful with using the second parameter $length!

down

-4

John ¶

16 years ago

And when retrieving mod_deflate gzip'ed content and using gzinflate() to decode the data, be sure to strip the first 11 chars from the retrieved content.



<?php $dec = gzinflate(substr($enc,11)); ?>

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gzinflate

Description

Parameters

Return Values

Examples

See Also

Found A Problem?

User Contributed Notes 10 notes