How to determine whether gzip compression is enabled on a web page in PHP

This article introduces how to use PHP code to determine whether gzip compression is enabled on a web page. Friends in need may wish to use it as a reference.

When collecting web pages, I found that the web pages obtained by file_get_contents were garbled when saved locally. The response header contained Content-Encoding: gzip, but it was normal when viewed in the browser.

From this, we can judge that the website has gzip turned on and file_get_contents obtains compressed pages instead of decompressed pages (I wonder if file_get_contents should bring corresponding parameters when requesting web pages to directly obtain web pages that have not been compressed by gzip? )

I have seen before that the file type can be determined by reading the first 2 bytes of the file. The first 2 bytes of a gzip-compressed web page (gbk encoded) are 1F 8B, which can be used to determine whether the web page has been gzip-compressed.

Example:

<?php
//gzip压缩网页 
//file_get_contents 直接获得的网页是乱码。 
header('Content-Type:text/html;charset=utf-8' ); 
$url = 'http://bbs.it-home.org'; 
$file = fopen($url, "rb");   
//只读2字节  如果为(16进制)1f 8b (10进制)31 139则开启了gzip ; 
$bin = fread($file, 2);  
fclose($file);   
$strInfo = @unpack("C2chars", $bin);   
$typeCode = intval($strInfo['chars1'].$strInfo['chars2']);   
$isGzip = 0;   
switch ($typeCode)   
{ 
    case 31139:       
      //网站开启了gzip 
        $isGzip = 1; 
        break; 
    default:   
        $isGzip = 0; 
}   
$url = $isGzip ? "compress.zlib://".$url:$url; // 三元表达式 
$mierHtml = file_get_contents($url); //获得数据 
$mierHtml = iconv("gbk","utf-8",$mierHtml); 
echo $mierHtml;
?>