有時候我們會在開發中，經常會遇到有URL 301或 302重定向的情況，這時候我們可能需要獲取重定向之後的url，下面我們介紹一下幾種獲取重定向url的方法：

1、用get_headers函式
php自帶的get_headers函式可以獲取伺服器響應一個HTTP請求所傳送的所有標頭，我們可以嘗試用該函式實現。

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、使用fsockopen()內建函式

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、使用cURL函式

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($ch, CURLOPT_NOBODY, TRUE);//不返回請求體內容
   curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);//允許請求的連結跳轉
   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);//設定referer
   }
   $content = curl_exec($ch);
   if(!curl_errno($ch)) {
     $redirect_url = curl_getinfo($ch, CURLINFO_EFFECTIVE_URL);//獲取最終請求的url地址
   }
   return $redirect_url;
}

哪個方法的效果更高一些，可以自行測試一下。

from：https://blog.csdn.net/zimuxin/article/details/52228917