Summary of various methods to implement GZIP compression output using zlib extension in PHP_PHP Tutorial

Under normal circumstances, when we have a large amount of data transmission and want to reduce the bandwidth pressure on the server, we will adopt a method to compress the file transmission. Using zlib in PHP can also achieve gzip compression output. Let's look at a summary of various methods of GZIP compression 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 it. php+apache+mysql operating environment.

php gzip configuration steps

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

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

modified to

zlib.output_compression = On
zlib.output_compression_level = 6

Example 1

PHP uses zlib extension to implement page GZIP compression output

Code

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The code is as follows

代码如下

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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

function ob_gzip($content) // $content is the page content to be compressed

{

if(!headers_sent() && extension_loaded("zlib") && strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip")) //Determine whether the page header information is output, whether the zlib extension in PHP has been loaded, and whether the browser supports GZIP technology

{

$content = gzencode($content." n//This page has been compressed",9 ); //Add the comment label "//This page has been compressed" to the content to be compressed, and then use the gzencode() function provided by zlib to perform compression at level 9. This parameter value range is 0-9, 0 means No compression, 9 means maximum compression. Of course, the higher the degree of compression, the more CPU is consumed.

//Use the header() function to send some header information to the browser to tell the browser that this page has been compressed with GZIP!

header(“Content-Encoding: gzip”);

header(“Vary: Accept-Encoding”);header(“Content-Length: “.strlen($content)); }

return $content; //Return the compressed content

代码如下	复制代码
//调用一个函数名为ob_gzip的内容进行压缩 ob_start('ob_gzip'); //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; } ?>

After the function is written, call it with ob_start, so the original ob_start() becomes Become 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 the bufferob_end_flush(); //End the buffer and output the 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

The code is as follows

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//Call a function named ob_gzip to compress the content<🎜>ob_start( 'ob_gzip');<🎜>//Output content<🎜>ob_end_flush();<🎜>//This is the ob_gzip function<🎜><🎜>function ob_gzip($content)<🎜>{<🎜>if(! headers_sent()&&extension_loaded("zlib")<🎜>&&strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip"))<🎜>{<🎜>$content = gzencode($content." n//This page has been compressed ",9);<🎜>header("Content-Encoding: gzip");<🎜>header("Vary: Accept-Encoding");<🎜>header("Content-Length: ".strlen($content) );<🎜>}<🎜>return $content;<🎜>}<🎜>?>

Example 2

Zlib compression and decompression swf file code

Example of file:

代码如下

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//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); //---------------------------------------------------------------------------------------------------- ?> 解压缩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); $head = "F".$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 by using the ob_gzhandler function on pages that need to be compressed and output. You can only choose one of the two, otherwise an error will be reported.

2. The default value of zlib.output_compression 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 is recommended Set the compression ratio to 6, and the optional range is 1-9, -1 means 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 the php gzip compression output configuration. Many netizens will say that I have enabled the php gzip configuration in the php.ini configuration file. The reason why php gzip compression is still not implemented is because apache is not loaded with deflate_module. The method is as follows, remove the # number at the beginning of

代码如下	复制代码
#LoadModule deflate_module modules/mod_deflate.so

and restart apache.