gzdecode()

(PHP 5 >= 5.4.0, PHP 7)

Decodes a gzip compressed string

说明

gzdecode(string $data[,int $length]): string

This function returns a decoded version of the input$data.

参数

$data

The data to decode, encoded by gzencode().

$length

The maximum length of data to decode.

返回值

The decoded string, or FALSE if an error occurred.

参见

• gzencode()Create a gzip compressed string

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.

I don't have any deep knowledge in compression algorithms and formats, so I have no idea if this works the same on all platforms. But by several experiments on my Linux box I found how to get gzdecoded data without temporary files. Here it is:
<?php
function gzdecode($data)
{
  return gzinflate(substr($data,10,-8));
}
?>
That's it. Simply strip header and footer bytes and you get raw deflated data for inflation.

3 more bugs found and fixed: 
1. failed to work when the gz contained a filename - FIXED
2. failed to work on 64-bit architecture (checksum) - FIXED
3. failed to work when the gz contained a comment - cannot verify. 
Returns some errors (not all!) and filename.
<?php function gzdecode($data,&$filename='',&$error='',$maxlength=null) 
{
  $len = strlen($data);
  if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
    $error = "Not in GZIP format.";
    return null; // Not GZIP format (See RFC 1952)
  }
  $method = ord(substr($data,2,1)); // Compression method
  $flags = ord(substr($data,3,1)); // Flags
  if ($flags & 31 != $flags) {
    $error = "Reserved bits not allowed.";
    return null;
  }
  // NOTE: $mtime may be negative (PHP integer limitations)
  $mtime = unpack("V", substr($data,4,4));
  $mtime = $mtime[1];
  $xfl  = substr($data,8,1);
  $os  = substr($data,8,1);
  $headerlen = 10;
  $extralen = 0;
  $extra   = "";
  if ($flags & 4) {
    // 2-byte length prefixed EXTRA data in header
    if ($len - $headerlen - 2 < 8) {
      return false; // invalid
    }
    $extralen = unpack("v",substr($data,8,2));
    $extralen = $extralen[1];
    if ($len - $headerlen - 2 - $extralen < 8) {
      return false; // invalid
    }
    $extra = substr($data,10,$extralen);
    $headerlen += 2 + $extralen;
  }
  $filenamelen = 0;
  $filename = "";
  if ($flags & 8) {
    // C-style string
    if ($len - $headerlen - 1 < 8) {
      return false; // invalid
    }
    $filenamelen = strpos(substr($data,$headerlen),chr(0));
    if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
      return false; // invalid
    }
    $filename = substr($data,$headerlen,$filenamelen);
    $headerlen += $filenamelen + 1;
  }
  $commentlen = 0;
  $comment = "";
  if ($flags & 16) {
    // C-style string COMMENT data in header
    if ($len - $headerlen - 1 < 8) {
      return false;  // invalid
    }
    $commentlen = strpos(substr($data,$headerlen),chr(0));
    if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
      return false;  // Invalid header format
    }
    $comment = substr($data,$headerlen,$commentlen);
    $headerlen += $commentlen + 1;
  }
  $headercrc = "";
  if ($flags & 2) {
    // 2-bytes (lowest order) of CRC32 on header present
    if ($len - $headerlen - 2 < 8) {
      return false;  // invalid
    }
    $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
    $headercrc = unpack("v", substr($data,$headerlen,2));
    $headercrc = $headercrc[1];
    if ($headercrc != $calccrc) {
      $error = "Header checksum failed.";
      return false;  // Bad header CRC
    }
    $headerlen += 2;
  }
  // GZIP FOOTER
  $datacrc = unpack("V",substr($data,-8,4));
  $datacrc = sprintf('%u',$datacrc[1] & 0xFFFFFFFF);
  $isize = unpack("V",substr($data,-4));
  $isize = $isize[1];
  // decompression:
  $bodylen = $len-$headerlen-8;
  if ($bodylen < 1) {
    // IMPLEMENTATION BUG!
    return null;
  }
  $body = substr($data,$headerlen,$bodylen);
  $data = "";
  if ($bodylen > 0) {
    switch ($method) {
    case 8:
      // Currently the only supported compression method:
      $data = gzinflate($body,$maxlength);
      break;
    default:
      $error = "Unknown compression method.";
      return false;
    }
  } // zero-byte body content is allowed
  // Verifiy CRC32
  $crc  = sprintf("%u",crc32($data));
  $crcOK = $crc == $datacrc;
  $lenOK = $isize == strlen($data);
  if (!$lenOK || !$crcOK) {
    $error = ( $lenOK ? '' : 'Length check FAILED. ') . ( $crcOK ? '' : 'Checksum FAILED.');
    return false;
  }
  return $data;
}
?>

Aaron G. 07-Aug-2004 03:29 posted the function gzdecode()
to gzencode comments. I FIXED the BUG: if($flags & 1) to the correct if($flags & 2)
Unfortunately the function gzencode() does NOT append a CRC so I did not notice until I tried to upload a file compressed with gzip itself.
<?php
function gzdecode($data) {
 $len = strlen($data);
 if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {
  return null; // Not GZIP format (See RFC 1952)
 }
 $method = ord(substr($data,2,1)); // Compression method
 $flags = ord(substr($data,3,1)); // Flags
 if ($flags & 31 != $flags) {
  // Reserved bits are set -- NOT ALLOWED by RFC 1952
  return null;
 }
 // NOTE: $mtime may be negative (PHP integer limitations)
 $mtime = unpack("V", substr($data,4,4));
 $mtime = $mtime[1];
 $xfl  = substr($data,8,1);
 $os  = substr($data,8,1);
 $headerlen = 10;
 $extralen = 0;
 $extra   = "";
 if ($flags & 4) {
  // 2-byte length prefixed EXTRA data in header
  if ($len - $headerlen - 2 < 8) {
   return false;  // Invalid format
  }
  $extralen = unpack("v",substr($data,8,2));
  $extralen = $extralen[1];
  if ($len - $headerlen - 2 - $extralen < 8) {
   return false;  // Invalid format
  }
  $extra = substr($data,10,$extralen);
  $headerlen += 2 + $extralen;
 }
 $filenamelen = 0;
 $filename = "";
 if ($flags & 8) {
  // C-style string file NAME data in header
  if ($len - $headerlen - 1 < 8) {
   return false;  // Invalid format
  }
  $filenamelen = strpos(substr($data,8+$extralen),chr(0));
  if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {
   return false;  // Invalid format
  }
  $filename = substr($data,$headerlen,$filenamelen);
  $headerlen += $filenamelen + 1;
 }
 $commentlen = 0;
 $comment = "";
 if ($flags & 16) {
  // C-style string COMMENT data in header
  if ($len - $headerlen - 1 < 8) {
   return false;  // Invalid format
  }
  $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));
  if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {
   return false;  // Invalid header format
  }
  $comment = substr($data,$headerlen,$commentlen);
  $headerlen += $commentlen + 1;
 }
 $headercrc = "";
 if ($flags & 2) {
  // 2-bytes (lowest order) of CRC32 on header present
  if ($len - $headerlen - 2 < 8) {
   return false;  // Invalid format
  }
  $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;
  $headercrc = unpack("v", substr($data,$headerlen,2));
  $headercrc = $headercrc[1];
  if ($headercrc != $calccrc) {
   return false;  // Bad header CRC
  }
  $headerlen += 2;
 }
 // GZIP FOOTER - These be negative due to PHP's limitations
 $datacrc = unpack("V",substr($data,-8,4));
 $datacrc = $datacrc[1];
 $isize = unpack("V",substr($data,-4));
 $isize = $isize[1];
 // Perform the decompression:
 $bodylen = $len-$headerlen-8;
 if ($bodylen < 1) {
  // This should never happen - IMPLEMENTATION BUG!
  return null;
 }
 $body = substr($data,$headerlen,$bodylen);
 $data = "";
 if ($bodylen > 0) {
  switch ($method) {
   case 8:
    // Currently the only supported compression method:
    $data = gzinflate($body);
    break;
   default:
    // Unknown compression method
    return false;
  }
 } else {
  // I'm not sure if zero-byte body content is allowed.
  // Allow it for now... Do nothing...
 }
 // Verifiy decompressed size and CRC32:
 // NOTE: This may fail with large data sizes depending on how
 //    PHP's integer limitations affect strlen() since $isize
 //    may be negative for large sizes.
 if ($isize != strlen($data) || crc32($data) != $datacrc) {
  // Bad format! Length or CRC doesn't match!
  return false;
 }
 return $data;
}
?>

if (!function_exists('gzdecode')) {
  function gzdecode($data)
  {
    return gzinflate(substr($data,10,-8));
  }
}

I have used this simple function to gzdecode gzipped files downloaded from the web.
<?php
function gzdecode($data){
 $g=tempnam('/tmp','ff');
 @file_put_contents($g,$data);
 ob_start();
 readgzfile($g);
 $d=ob_get_clean();
 return $d;
}
?>

katzlbtjunk (2008-04-30), thanks for code. But remember, .gz file may be series of members (data sets). They should be uncompressed in loop.
Fixed code gzdecodeM() on http://gist.github.com/msegu/de556cdd32eb58430871b06145168024
Addicionally, you can
- get data of gz members in array
- choose members you need to extract

This can help to decompress the data from tar archive in certain cases, hope this helps somebody
<?php
$tarName = 'example.ini';
try {
  /** For files with tar.gz extensions **/
  $phar = new \PharData($path, 0, $tarName);
} catch ($e) {
  /** Decode the file first **/
  $decodedFile = file_put_contents($path, gzdecode(file_get_contents($path)));
  /** create PharData object second **/
  $phar = new \PharData($path, 0, $tarName);
}
?>

In my case to decode correctly a GZIPOutputStream POST from Android I used 
gzinflate( substr($post,10,-8) );
and not 
gzinflate( substr($HTTP_RAW_POST_DATA,10,-8) ) . PHP_EOL . PHP_EOL

I use the following code:
function &gzdecodedata(&$data) {
  ob_start();
  readgzfile('data://application/gzip;base64,' . base64_encode($data));
  $d = ob_get_clean();
  return $d;
}