php 获取301 302的真实地址

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