Detailed explanation of GZIP compression function on PHP zlib extension page_PHP tutorial

To implement GZIP compressed pages, the browser and the server need to support each other. 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.

It’s a bit wordy, let’s get down to business:

Just like to make compressed biscuits, 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 that comes with PHP to make one:

The code is as follows:

function ob_gzip($content) // $content is to compress The page content, or cookie ingredients
{
if( !headers_sent() && // If the page header information has not been output yet
extension_loaded("zlib") && // And the zlib extension has been loaded to In PHP
strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip")) //And the browser says it can accept GZIP pages
{
$content = gzencode($content." //This page has been compressed",9); Attach 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 It is 0-9, 0 means no compression, and 9 means maximum compression. Of course, the higher the degree of compression, the more CPU it will cost.

//Then use the header() function to send some header information to the browser to tell the browser. 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 biscuits back to the workbench.

The compressor is ready. After that, we put the compressor on the workbench, so the original ob_start() becomes

ob_start(ob_gzip); //Yes, we just add a parameter to ob_start(), and the parameter name is ours The function name of the "compressor" just made. In this way, when the content enters the buffer, PHP will call the ob_gzip function to compress it.
Okay, all the work is completed, and the final delivery is:

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:

Code. As follows:

//Enable a workbench with ob_gzip compressor
ob_start(ob_gzip);
//Prepare some content to be compressed
for ($i=0; $i<100; $i )
{
echo(Here are the raw materials for compressed biscuits, here are the raw materials for compressed biscuits, raw materials);
}
// Output Compression result
ob_end_flush();
//This is ob_gzip compressor
function ob_gzip($content)
{
if( !headers_sent() &&
extension_loaded("zlib" ) &&
strstr($_SERVER["HTTP_ACCEPT_ENCODING"],"gzip"))
{
$content = gzencode($content." //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, reduced to 104B after enabling GZIP. Uh... I may not be good at math. I'll calculate how much it is compressed to.

In addition, the following is obtained using FlashGet. In the log information, you can see the header information added to our program:

The code is as follows:

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 :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

http://www.bkjia.com/PHPjc/486206.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/486206.htmlTechArticleTo implement GZIP compression page, the browser and server need to support it. In fact, it is server compression. After it is transmitted to the browser The browser decompresses and parses it. We don’t need to worry about the browser,...