PHP uses zlib extension to implement page GZIP compression output_PHP tutorial

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!
To implement GZIP compressed pages, the browser and the server need to support it. In fact, it is server compression. After being transmitted to the browser, the browser decompresses and parses it. We don’t need to worry about the browser, because most browsers now support parsing GZIP pages. We just need to compress the page on the server side and then output it to the browser.

This is a bit wordy, let’s get down to business:
Just like to make compressed cookies, you must first get the raw materials, and to compress a page, you must first obtain the content to be output. The ob_start() (ob => output buffer) function in PHP can achieve this function. It can first put the content to be output in the program into a place called "buffer". Of course, you can understand it as making compressed cookies. A workbench for temporarily placing raw materials.
This function must be used before the page is output, so it is generally placed at the top of the code. Because it is like a workbench, you have to prepare it before the raw materials arrive, otherwise there will be no place to put the raw materials when they arrive, and problems will occur. After using ob_start() to get the page to be compressed, we can make compressed cookies. No, the page should be compressed! But it seems that there is still a lack of a compressor, EZ, we use the zlib extension of PHP to make one:

​ function ob_gzip($content) // $content is the page content to be compressed, or biscuit ingredients
{ 
If( !headers_sent() && // If the page header information has not been output yet
          extension_loaded("zlib") && // And the zlib extension has been loaded into PHP
          strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip")) //And the browser says it can accept GZIP pages
{
$content = gzencode($content." n//This page has been compressed",9); Attach a comment label "//This page has been compressed" to the content to be compressed, and then execute it with the gzencode() function provided by zlib For compression level 9, the value range of this parameter is 0-9, 0 means no compression, and 9 means maximum compression. Of course, the higher the degree of compression, the more CPU is consumed.
                                                 ​​​​//Then use the header() function to send some header information to the browser, telling 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, or send the compressed cookies back to the workbench.
}

After the compressor is ready, we put the compressor on the workbench, so the original ob_start() becomes
​ ob_start('ob_gzip'); //Yes, just add a parameter to ob_start(), and the parameter name is the function name of the "compressor" we just made. In this way, when the content enters the buffer, PHP will call the ob_gzip function to compress it.

Well, all the work is done, final delivery:
​ ob_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.

The complete example is as follows:
​ //Enable a workbench with ob_gzip compressor
ob_start('ob_gzip');
//Prepare some content to be compressed
for($i=0; $i<100; $i++)
{
echo('Here are the raw materials for compressed biscuits, here are the raw materials for compressed biscuits, raw materials');
}
//Output the compression result
ob_end_flush();
//This is ob_gzip compressor
function ob_gzip($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;
}
?>

After actual testing, if GZIP is not used in the above code, it is 4.69KB = 4802.56B. After enabling GZIP, it is reduced to 104B
. Uh... I may not be good at math. I will calculate the percentage of the original compression. .
In addition, the following is the log information obtained using FlashGet. You can see the header information added to our program:
QUOTE: Fri Jan 25 17:53:10 2008 HTTP/1.1 200 OK

Fri Jan 25 17:53:10 2008 Server: Microsoft-IIS/5.1
Fri Jan 25 17:53:10 2008 Date: Fri, 25 Jan 2008 09:53:10 GMT
Fri Jan 25 17:53:10 2008 Connection: close
Fri Jan 25 17:53:10 2008 X-Powered-By: PHP/5.2.5
Fri Jan 25 17:53:10 2008 Content-Encoding: gzip
Fri Jan 25 17:53:10 2008 Vary: Accept-Encoding
Fri Jan 25 17:53:10 2008 Content-Length: 104
Fri Jan 25 17:53:10 2008 Content-type: text/html