ESP8266WebServer cookie save problem

[blh64]

@phvg

  String cookieHeader = "Set-Cookie: " + String(cookieName) + "=" + String(cookieValue);
  if (days > 0) {cookieHeader += ";expires=" + String(days * 24 * 60 * 60) + ";";     // Add expiration if days is greater than 0
  }
  server.sendHeader("Set-Cookie", cookieHeader);               // Send the cookie header to the client

How can that be a typo?

Your string cookieHeader contains "Set-Cookie: ....." and then the .sendHeader() call uses the header "Set-Cookie" and the value is your cookieHeader String?