gzdecode

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;
}
?>

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;
}
?>

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);
}
?>