Detailed explanation of how PHP uses zlib extension to implement GZIP compressed output

This article mainly introduces the method of PHP using zlib extension to achieve GZIP compression output. It analyzes in detail the related operation skills of PHP gzip configuration and compression output in the form of examples. Friends in need can refer to this article

The example describes how PHP uses the zlib extension to implement GZIP compressed output. Share it with everyone for your reference, the details are as follows:

Generally, when we have a large amount of data transmission and hope to reduce the bandwidth pressure on the server, we will adopt a method to compress the file transmission. Using zlib in PHP can also implement gzip Compressed output, let’s look at a summary of various methods of GZIP compressed output.

GZIP (GNU-ZIP) is a compression technology. After GZIP compression, the page size can be reduced to 30% or even smaller than the original size. In this way, users will feel refreshed and happy when browsing!

Preparation

1. Can’t find the php_zlib.dll file?

Zlib compression has been built into php since php4.3, so at least in Windows environment there is no need to install zlib.

2. Install and build the php running environment

Since it is not enough to enable gzip configuration through the php.ini configuration file to achieve php gzip compression output, it requires the support of apache, so it is recommended to install and build php apache mysql operating environment.

php gzip configuration steps

1. Open the php.ini configuration file and find zlib.output_compression = Off, Change

zlib.output_compression = Off
;zlib.output_compression_level = -1

to

zlib.output_compression = On
zlib.output_compression_level = 6

Example 1

PHP uses zlib extension to implement page GZIP compression output

Code

function ob_gzip($content) // $content 就是要压缩的页面内容
{
if(!headers_sent() && extension_loaded("zlib") && strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip"))//判断页面头部信息是否输出，PHP中zlib扩 展是否已经加载，浏览器是否支持GZIP技术
{
$content = gzencode($content." n//此页已压缩",9); //为准备压缩的内容贴上"//此页已压缩"的注释标签，然后用zlib提供的gzencode()函数执行级别为9的压缩，这个参数值范围是0-9，0 表示无压缩，9表示最大压缩，当然压缩程度越高越费CPU。
//用header()函数给浏览器发送一些头部信息，告诉浏览器这个页面已经用GZIP压缩过了！
header("Content-Encoding: gzip");
header("Vary: Accept-Encoding");
header("Content-Length: ".strlen($content));
}
return $content; //返回压缩的内容

After the function is written, call it with ob_start , so the original ob_start() becomes

Copy code The code is as follows:

ob_start(' ob_gzip'); //Add a parameter to ob_start(), and the parameter name is the function name just now. In this way, when the content enters the buffer, PHP will call the ob_gzip function to compress it.

Finally end buffer

Copy code The code is as follows:

ob_end_flush(); //End buffer area, output content. Of course, you don't need this function, because the buffer content will be automatically output at the end of the program execution.

Final complete example

<?php
//调用一个函数名为ob_gzip的内容进行压缩
ob_start(&#39;ob_gzip&#39;);
//输出内容
ob_end_flush();
//这是ob_gzip函数
function ob_gzip($content)
{
if(!headers_sent()&&extension_loaded("zlib")
&&strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip"))
{
$content = gzencode($content." n//此页已压缩",9);
header("Content-Encoding: gzip");
header("Vary: Accept-Encoding");
header("Content-Length: ".strlen($content));
}
return $content;
}
?>

Example 2

zlib compression and decompression of swf files Code

Example of file:

//没有加入判断swf文件是否已经压缩,入需要可以根据文件的第一个字节是'F'或者'C'来判断
压缩swf文件:
//--------------------------------------------------------------------------------------------------
//文件名
$filename = "test.swf";
//打开文件
$rs = fopen($filename,"r");
//读取文件的数据
$str = fread($rs,filesize($filename));
//设置swf头文件
$head = substr($str,1,8);
$head = "C".$head;
//获取swf文件内容
$body = substr($str,8);
//压缩文件内容,使用最高压缩级别9
$body = gzcompress($body, 9);
//合并文件头和内容
$str = $head.$body;
//关闭读取的文件流
fclose($rs);
//创建一个新的文件
$ws = fopen("create.swf","w");
//写文件
fwrite($ws,$str);
//关闭文件留
fclose($ws);
//----------------------------------------------------------------------------------------------------
?>

Unzip swf file:

//----------------------------------------------------------------------------------------------------
//文件名
$filename = "test.swf";
//打开文件
$rs = fopen($filename,"r");
//读取文件的数据
$str = fread($rs,filesize($filename));
//设置swf头文件
$head = substr($str,1,8);
$head = "F".$head;
//获取swf文件内容
$body = substr($str,8);
//解压缩文件内容
$body = gzuncompress($body);
//合并文件头和内容
$str = $head.$body;
//关闭读取的文件流
fclose($rs);
//创建一个新的文件
$ws = fopen("create.swf","w");
//写文件
fwrite($ws,$str);
//关闭文件留
fclose($ws);
//----------------------------------------------------------------------------------------------------
?>

Example 3

Enable php zlib (gzip) compression output

php gzip configuration knowledge points:

1. By default, PHP does not enable zlib whole-site compression output, but uses the ob_gzhandler function on pages that require compressed output. You can only choose one of the two, otherwise an error will be reported.

2, zlib.output_compressionThe default value is Off, you can set it to On, or output buffer size (default is 4k)

3, zlib.output_compression_level represents the compression ratio. The default recommended compression ratio is 6. The optional range is 1-9. -1 represents turning off php zlib (gzip) compression

2. Save the php.ini configuration file , and restart the apache server

3. Open the apache configuration file httpd.conf, configure and load deflate_module

This step is the most critical step to enable php gzip compression output configuration. Many netizens will say that even though I have enabled the php gzip configuration in the php.ini configuration file, I still don’t realize php gzip compression. This is because apache is not loaded with deflate_module. The method is as follows, change

#LoadModule deflate_module modules/mod_deflate.so

Remove the # sign at the beginning and restart apache.

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