private static function sendHeader($key, $value) {
    if (isset(self::$send_header)) {
      call_user_func(self::$send_header, $key, $value);
    } else {
      header(sprintf("%s: %s", $key, $value));
    }
  }
private static function sendHeader($key, $value) {
    if (isset(self::$send_header)) {
      call_user_func(self::$send_header, $key, $value);
    } else {
      header(sprintf("%s: %s", $key, $value));
    }
  }
private static function sendHeader ( $ key , $ value ) { if ( isset ( self :: $ send_header ) ) { call_user_func ( self :: $ send_header , $ key , $ value ) ; } else { header ( sprintf ( "%s: %s" , $ key , $ value ) ) ; } }
SendHeader hook, used for testing.

@param string $key The header key.
@param string $value The header value.

@access private
SendHeader hook used for testing .