<?php

// News: I had once said that when PHP4.0.5 comes out I will reccomend the built in
// ob_gzhandler over my code unless you are generating flash or images on the fly.
//
// I was wrong. PHP4.0.5 is out and ob_gzhandler doesn't work for me.

// Note: This is rather cool: http://Leknor.com/code/gziped.php
// It will calculate the effects of this class on a page.
// compression level, cpu time, download time, etc

// Note: this may better for some sites:
// http://www.remotecommunications.com/apache/mod_gzip/
// I've read that the above doesn't work with php output.

class gzip_encode {
/*
* gzip_encode - a class to gzip encode php output
*
* By Sandy McArthur, Jr.
*
* Copyright 2001 (c) All Rights Reserved, All Responsibility Yours.
*
* This code is released under the GNU LGPL Go read it over here:
* http://www.gnu.org/copyleft/lesser.html
*
* I do make one optional request, I would like an account on or a
* copy of where this code is used. If that is not possible then
* an email would be cool.
*
* How to use:
* 1. Output buffering has to be turned on. You can do this with ob_start()
* <http://php.net/manual/function.ob-start.php> or in the php config
* file. Nothing bad happens if output buffering isn't turned on, your
* page just won't get compressed.
* 2. Include the class file.
* 3. At the _very_ end of your script create an instance of the encode
* class.
*
* eg:
* ------------Start of file----------
* |<?php
* | ob_start();
* | include('class.gzip_encode.php');
* |?>
* |
* |... the page ...
* |
* |<?php
* | new gzip_encode();
* |?>
* -------------End of file-----------
*
* Things to note:
* 1. There is no space before the beginning of the file and the '<?php' tag
* 2. The ob_start() line is optional if output buffering is turned on in
* the main config file.
* 3. Turning on and off output buffering just won't work.
* 4. There must be nothing after the last '?>' tag at the end of the file.
* Be careful of a space hiding there.
* 5. There are better ways to compress served content but I think this is
* the only way to compress php output.
* 6. Your auto_prepend_file is a good place for the ob_start() and
* your auto_append_file is a good place for new gzip_encode().
* 7. If you put new gzip_encode() in your auto.append file then you can
* call ob_end_flush() in your script to disable compression.
*
* This was written from scratch from info freely available on the web.
*
* These site(s) were useful to me:
* http://www.php.net/manual/
* http://www.ietf.org/rfc/rfc2616.txt (Sections: 3.5, 14.3, 14.11)
*
* Requirments:
* PHP 4.0.1+: I use the '===' operator, and output buffering, crc32();
* zlib: Needed for the gzip encoding. (Odds are you have it)
*
* Benchmarks:
* Take a look at http://Leknor.com/code/gziped.php and feed it a page to
* get an idea of how it will preform on your data or page.
*
* To Do:
* 1. I have reports of no content errors. I can't seem to duplicate this.
* Please visit my discussion boards if you think you may be able to help
* 2. The Accept-Encoding isn't handled to spec. Check out 14.3 in RFC 2616
* to see how it should be done.
*
* Change Log:
* 0.67: Added Vary header to aid in caching.
* 0.66: Big bug fix. It wouldn't compress when it should.
* 0.65: Fix for PHP-4.0.5 suddenly removing the connection_timeout() function.
* 0.62: Fixed a typo
* 0.61: Detect file types more like described in the magic number files, also
* added detection for gzip and pk zip files.
* 0.6: Detect common file types that shouldn't be compressed, mainly
* for images and swf (Shockwave Flash doesn't really accept gzip)
* 0.53: Made gzip_accepted() method so everyone can detect if a page
* will be gzip'ed with ease.
* 0.52: Detection and graceful handling of improper install/missing libs
* 0.51: Added FreeBSD load average detection.
* 0.5: Passing true as the first parameter will try to calculate the
* compression level from the server's load average. Passing true
* as the second parameter will turn on debugging.
* 0.4: No longer uses a temp file to compress the output. Should speed
* thing up a bit and reduce wear on your hard disk. Also test if
* the http headers have been sent.
* 0.31: Made a small change to the tempnam() line to hopefully be more
* portable.
* 0.3: Added code for the 'x-gzip'. This is untested, I don't know of
* any browser that uses it but the RFC said to look out for it.
* 0.2: Checks for 'gzip' in the Accept-Encoding header
* 0.1: First working version.
*
* Thanks To (Suggestions and stuff):
* ?@boas.anthro.mnsu.edu http://php.net/manual/function.gzcompress.php
* Kaoslord
* Michael R. Gile
* Christian Hamm
* Anil Madhavapeddy
*
* The most recent version is available at:
* http://Leknor.com/code/
*
*/

var $_version = 0.67; // Version of the gzip_encode class

var $level; // Compression level
var $encoding; // Encoding type
var $crc; // crc of the output
var $size; // size of the uncompressed content
var $gzsize; // size of the compressed content

/*
* gzip_encode constructor - gzip encodes the current output buffer
* if the browser supports it.
*
* Note: all arguments are optionial.
*
* You can specify one of the following for the first argument:
* 0: No compression
* 1: Min compression
* ... Some compression (integer from 1 to 9)
* 9: Max compression
* true: Determin the compression level from the system load. The
* higher the load the less the compression.
*
* You can specify one of the following for the second argument:
* true: Don't actully output the compressed form but run as if it
* had. Used for debugging.
*/
function gzip_encode($level = 3, $debug = false) {
global $HTTP_ACCEPT_ENCODING;
if (!function_exists('gzcompress')) {
trigger_error('gzcompress not found, ' .
'zlib needs to be installed for gzip_encode',
E_USER_WARNING);
return;
}
if (!function_exists('crc32')) {
trigger_error('crc32() not found, ' .
'PHP >= 4.0.1 needed for gzip_encode', E_USER_WARNING);
return;
}
if (headers_sent()) return;
if (connection_status() !== 0) return;
$encoding = $this->gzip_accepted();
if (!$encoding) return;
$this->encoding = $encoding;

if ($level === true) {
$level = $this->get_complevel();
}
$this->level = $level;

$contents = ob_get_contents();
if ($contents === false) return;

$gzdata = "\x1f\x8b\x08\x00\x00\x00\x00\x00"; // gzip header
$size = strlen($contents);
$crc = crc32($contents);
$gzdata .= gzcompress($contents, $level);
$gzdata = substr($gzdata, 0, strlen($gzdata) - 4); // fix crc bug
$gzdata .= pack("V",$crc) . pack("V", $size);

$this->size = $size;
$this->crc = $crc;
$this->gzsize = strlen($gzdata);

if ($debug) {
return;
}

ob_end_clean();
Header('Content-Encoding: ' . $encoding);
Header('Vary: Accept-Encoding');
Header('Content-Length: ' . strlen($gzdata));
Header('X-Content-Encoded-By: class.gzip_encode '.$this->_version);

echo $gzdata;
}


/*
* gzip_accepted() - Test headers for Accept-Encoding: gzip
*
* Returns: if proper headers aren't found: false
* if proper headers are found: 'gzip' or 'x-gzip'
*
* Tip: using this function you can test if the class will gzip the output
* without actually compressing it yet, eg:
* if (gzip_encode::gzip_accepted()) {
* echo "Page will be gziped";
* }
* note the double colon syntax, I don't know where it is documented but
* somehow it got in my brain.
*/
function gzip_accepted() {
global $HTTP_ACCEPT_ENCODING;
if (strpos($HTTP_ACCEPT_ENCODING, 'gzip') === false) return false;
if (strpos($HTTP_ACCEPT_ENCODING, 'x-gzip') === false) {
$encoding = 'gzip';
} else {
$encoding = 'x-gzip';
}

// Test file type. I wish I could get HTTP response headers.
$magic = substr(ob_get_contents(),0,4);
if (substr($magic,0,2) === '^_') {
// gzip data
$encoding = false;
} else if (substr($magic,0,3) === 'GIF') {
// gif images
$encoding = false;
} else if (substr($magic,0,2) === "\xFF\xD8") {
// jpeg images
$encoding = false;
} else if (substr($magic,0,4) === "\x89PNG") {
// png images
$encoding = false;
} else if (substr($magic,0,3) === 'FWS') {
// Don't gzip Shockwave Flash files. Flash on windows incorrectly
// claims it accepts gzip'd content.
$encoding = false;
} else if (substr($magic,0,2) === 'PK') {
// pk zip file
$encoding = false;
}

return $encoding;
}

/*
* get_complevel() - The level of compression we should use.
*
* Returns an int between 0 and 9 inclusive.
*
* Tip: $gzleve = gzip_encode::get_complevel(); to get the compression level
* that will be used with out actually compressing the output.
*
* Help: if you use an OS other then linux please send me code to make
* this work with your OS - Thanks
*/
function get_complevel() {
$uname = posix_uname();
switch ($uname['sysname']) {
case 'Linux':
$cl = (1 - $this->linux_loadavg()) * 10;
$level = (int)max(min(9, $cl), 0);
break;
case 'FreeBSD':
$cl = (1 - $this->freebsd_loadavg()) * 10;
$level = (int)max(min(9, $cl), 0);
break;
default:
$level = 3;
break;
}
return $level;
}

/*
* linux_loadavg() - Gets the max() system load average from /proc/loadavg
*
* The max() Load Average will be returned
*/
function linux_loadavg() {
$buffer = "0 0 0";
$f = fopen("/proc/loadavg","r");
if (!feof($f)) {
$buffer = fgets($f, 1024);
}
fclose($f);
$load = explode(" ",$buffer);
return max((float)$load[0], (float)$load[1], (float)$load[2]);
}

/*
* freebsd_loadavg() - Gets the max() system load average from uname(1)
*
* The max() Load Average will be returned
*
* I've been told the code below will work on solaris too, anyone wanna
* test it?
*/
function freebsd_loadavg() {
$buffer= `uptime`;
ereg("averag(es|e): ([0-9][.][0-9][0-9]), ([0-9][.][0-9][0-9]), ([0-9][.][0-9][0-9]*)", $buffer, $load);

return max((float)$load[2], (float)$load[3], (float)$load[4]);
}
}

?>
这里的mod_gzip和apache
里面实现的mod_gzip原理上是一样的
但是apache的实现的效率会更高
大家可以安装一个apache的这个
mod_gzip 看看
用ab测试以后你会看到他的压缩以后的页面
会很小了