获取URL列表的重定向位置

Question

我有一个包含网址列表的txt文件。我想要该列表中所有URL的重定向位置。 这是我的代码：

$url_list = "ggurl.txt";


$ch = curl_init();

curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

foreach (file($url_list) as $url) {

    curl_setopt($ch, CURLOPT_URL, $url);
    $out = curl_exec($ch);

    // line endings is the wonkiest piece of this whole thing
    $out = str_replace("\r", "", $out);

    // only look at the headers
    $headers_end = strpos($out, "\n\n");
    if( $headers_end !== false ) { 
        $out = substr($out, 0, $headers_end);
    }   

    $headers = explode("\n", $out);
    foreach($headers as $header) {
        if( substr($header, 0, 10) == "Location: " ) { 
            $target = substr($header, 10);

            echo "[$url] redirects to [$target]<br>";
            $url = $target;
            continue 2;
        }
    }

$url = rtrim($url);

echo $url . "<br>";

}

此代码的问题在于它仅显示列表中最后一个URL的重定向位置。有谁知道这个问题的解决方案？