php 监测远道文件是否存在

function remote_file_exists($url_file){     $url_file = trim($url_file);     if (empty($url_file)) return false;     $url_arr = parse_url($url_file);     if (!is_array($url_arr) || empty($url_arr)) return false;     $host = $url_arr['host'];     $path = $url_arr['path'] ."?".$url_arr['query'];     $port = isset($url_arr['port']) ?$url_arr['port'] : "80";     $fp = fsockopen($host, $port, $err_no, $err_str,30);     if (!$fp) return false;     $request_str = "GET ".$path." HTTP/1.1\r\n";     $request_str .= "Host:".$host."\r\n";     $request_str .= "Connection:Close\r\n\r\n";     fwrite($fp,$request_str);      $first_header = fread($fp, 128);     fclose($fp);     if (trim($first_header) == "") return false;     if (!preg_match("/200/", $first_header) || preg_match("/Location:/", $first_header)) return false;     return true; }