php获取301跳转URL简单实例

　　/**

　　* get_redirect_url()

　　* Gets the address that the provided URL redirects to,

　　* or FALSE if there's no redirect.

　　*

　　* @param string $url

　　* @return string

　　*/

　　function get_redirect_url($url){

　　$redirect_url = null;

　　$url_parts = @parse_url($url);

　　if (!$url_parts) return false;

　　if (!isset($url_parts['host'])) return false; //can't process relative URLs

　　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)){

　　if ( substr($matches[1], 0, 1) == "/" )

　　return $url_parts['scheme'] . "://" . $url_parts['host'] . trim($matches[1]);

　　else

　　return trim($matches[1]);

　　} else {

　　return false;

　　}

　　}

　　/**

　　* get_all_redirects()

　　* Follows and collects all redirects, in order, for the given URL.

　　*

　　* @param string $url

　　* @return array

　　*/

　　function get_all_redirects($url){

　　$redirects = array();

　　while ($newurl = get_redirect_url($url)){

　　if (in_array($newurl, $redirects)){

　　break;

　　}

　　$redirects[] = $newurl;

　　$url = $newurl;

　　}

　　return $redirects;

　　}