gzuncompress

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);
 }
?>

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.

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));
 }
}
?>

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:
 */
$uncompressed = gzuncompress(substr($compressed, 4));
?>

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

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
$uncompressed = shell_exec("cat $compressed_file | zpipe -d");
?>

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 

Reading an ID3v2.3+ tag it is versy useful, because these tag's frames might be compressed. Zlib compressed frame layout (ID3v2.3):
Descriptior Size
-------------------
Frameheader:
Frame id: 4 bytes
Frame size (full frame size - frameheader size): 4 bytes
Frame flags: 2 bytes
 The 2nd byte's 7th bit must be 1 (e.g.: %1xy00000)
Frame content decrompessed size: 4 bytes
--------------------
Framecontent:
Compressed string described in 'frame size'
<?php
$frame="[read from a mp3 file]";
$frame_id=substr($frame,0,4);
/*....*/
$cs=substr($frame,10,4);
$checksize=$cs[3]*16777216+$cs[2]*65536+$cs[1]*256+$cs[0];
$content=substr($frame,14,$contentsize);
$content=gzuncompress($content);
if(strlen($content)!=$checksize){
 echo 'Error whil uncrompessing frame data<br>';
}
echo $content;
?>