PHP determines whether the page file has been compressed by gzip

<?php
ob_start(&#39;ob_gzhandler&#39;); // 开启gzip，屏蔽则关闭

$data = array(
 array(&#39;name&#39;=>&#39;one&#39;,&#39;value&#39;=>1),
 array(&#39;name&#39;=>&#39;two&#39;,&#39;value&#39;=>2),
 array(&#39;name&#39;=>&#39;three&#39;,&#39;value&#39;=>3)
);

header(&#39;content-type:application/json&#39;);
echo json_encode($data);
?>

<?php
$url = &#39;http://www.example.com/&#39;;
var_dump(check_gzip($url));

/**
 * 判断url是否经过gzip压缩
 * @param String $url 来源
 * @param Boolean
 */
function check_gzip($url){
 $header = get_headers($url, 1);
 if(isset($header[&#39;Vary&#39;]) && $header[&#39;Vary&#39;]==&#39;Accept-Encoding&#39;){
  return true;
 }
 return false;
}
?>

<?php
header(&#39;content-type:image/jpeg&#39;);
ob_start(&#39;ob_gzhandler&#39;); // 开启gzip，屏蔽则关闭
echo file_get_contents(&#39;test.jpg&#39;);
?>

<?php
$url = &#39;http://www.example.com/&#39;;
var_dump(check_gzip($url));

/**
 * 判断url是否经过gzip压缩
 * @param String $url 来源
 * @param Boolean
 */
function check_gzip($url){
 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL, $url);
 curl_setopt($ch, CURLOPT_HEADER, 1);   // 输出header信息
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); // 返回的信息不直接输出
 curl_setopt($ch, CURLOPT_ENCODING, &#39;&#39;);  // 不限制编码类型
 $response = curl_exec($ch);
 if(!curl_errno($ch)){
  $info = curl_getinfo($ch);
  // 获取header
  $header_size = $info[&#39;header_size&#39;];
  $header_str = substr($response, 0, $header_size);
  $filter = array("\r\n", "\r");
  $header_str = str_replace($filter, PHP_EOL, $header_str);

  // 检查content-encoding
  preg_match(&#39;/Content-Encoding: (.*)\s/i&#39;, $header_str, $matches);
  if(isset($matches[1]) && $matches[1]==&#39;gzip&#39;){
   return true;
  }
 }
 return false;
}
?>