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/1.1rn";
$request .= 'Host: ' . $url_parts['host'] . "rn";
$request .= "Connection: Closernrn";
fwrite($sock,$request);
$response = '';
while(!feof($sock)) $response .= fread($sock,8192);
fclose($sock);
if (preg_match('/^Location: (.+?)$/m',$response,$matches)){
if ( substr($matches[1],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;
}