PHP通过URL获取文件大小

 function getFileSize($url){
         $url = parse_url($url);
         if($fp = @fsockopen($url['host'],empty($url['port'])?80:$url['port'],$error)){
          fputs($fp,"GET ".(empty($url['path'])?'/':$url['path'])." HTTP/1.1\r\n");
          fputs($fp,"Host:$url[host]\r\n\r\n");
          while(!feof($fp)){
           $tmp = fgets($fp);
           if(trim($tmp) == ''){
            break;
           }else if(preg_match('/Content-Length:(.*)/si',$tmp,$arr)){
            return trim($arr[1]);
           }
          }
          return null;
         }else{
          return null;
         }
        }