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 format1) Data sent from Java Android app to PHP using DeflaterOutputStream java class and received in PHP as shown belowecho gzinflate( substr($HTTP_RAW_POST_DATA,2,-4) ) . PHP_EOL  . PHP_EOL;2) Data sent from Java Android app to PHP using GZIPOutputStream java class and received in PHP code as shown belowecho gzinflate( substr($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())<?phpif (!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.

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 bytesFrame size (full frame size - frameheader size): 4 bytesFrame 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;?>

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