What are the several ways to get the redirect URL in PHP

PHP method to obtain redirect URL: 1. Use get_headers function to obtain, syntax "get_headers($url, 1)"; 2. Use fsockopen() function to obtain; 3. Use curl_init(), curl_setopt() and other functions to obtain.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

1. Use the get_headers function
The get_headers function that comes with php can get all the headers sent by the server in response to an HTTP request. We can try to use this function to implement it.

function get_redirect_url($url){
   $header = get_headers($url, 1);
   if (strpos($header[0], ’301′) !== false || strpos($header[0], ’302′) !== false) {
     if(is_array($header['Location'])) {
       return $header['Location'][count($header['Location'])-1];
     }else{
       return $header['Location'];
        }
   }else {
     return $url;
   }
 }

2. Use the fsockopen() built-in function

function get_redirect_url($url){
   $redirect_url = false;
   $url_parts = @parse_url($url);
   if (!$url_parts) return false;
   if (!isset($url_parts['host'])) return false;
   if (!isset($url_parts['path'])) $url_parts['path'] = ‘/’;
   $sock = fsockopen($url_parts['host'], (isset($url_parts['port']) ?   (int)$url_parts['port'] : 80), $errno, $errstr, 30);
   if (!$sock) return false;
  $request = “HEAD ” . $url_parts['path'] . (isset($url_parts['query']) ? ‘?’.$url_parts['query'] : ”) . ” HTTP/1.1\r\n”;
   $request .= ‘Host: ‘ . $url_parts['host'] . “\r\n”;
   $request .= “Connection: Close\r\n\r\n”;
   fwrite($sock, $request);
   $response = ”;
   while(!feof($sock)) $response .= fread($sock, 8192);
   fclose($sock);
  if (preg_match(‘/^Location: (.+?)$/m’, $response, $matches)){
     return trim($matches[1]);
   } else {
    return false;
  }
}

3. Use the cURL function

function get_redirect_url($url, $referer=”, $timeout = 10) {
   $redirect_url = false;
   $ch = curl_init();
   curl_setopt($ch, CURLOPT_URL, $url);
   curl_setopt($ch, CURLOPT_HEADER, TRUE);
   curl_setopt($ch, CURLOPT_NOBODY, TRUE);//不返回请求体内容
   curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);//允许请求的链接跳转
   curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
   curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);
   curl_setopt($ch, CURLOPT_HTTPHEADER, array(
      ‘Accept: */*’,
      ‘User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)’,
      ‘Connection: Keep-Alive’));
   if ($referer) {
     curl_setopt($ch, CURLOPT_REFERER, $referer);//设置referer
   }
   $content = curl_exec($ch);
   if(!curl_errno($ch)) {
     $redirect_url = curl_getinfo($ch, CURLINFO_EFFECTIVE_URL);//获取最终请求的url地址
   }
   return $redirect_url;
}

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