HTTP headers automatically set

Question

I am starting to learn about http correctly.

I am working in lamp stack.

On the command line i am requesting a local page which will be served with apache to see the headers that are returned.

curl -i local.testsite

The page i am requesting has no content and i am not setting any headers but there are already a lot of headers sent in the response such as:

HTTP/1.1 200 OK
Date: Thu, 17 Jan 2013 20:28:52 GMT
Server: Apache/2.2.22 (Ubuntu)
X-Powered-By: PHP/5.3.10-1ubuntu3.4
Vary: Accept-Encoding
Content-Length: 0
Content-Type: text/html

So if i am not setting these, does apache set these automatically?

Answer 1

Some are set by PHP:

• The X-Powered-By header is set by the expose_php INI setting.
• The Content-Type header is set by the default_mimetype INI setting.

The others are set by Apache:

• The Server header is set by the ServerSignature directive.
• The Vary: Accept-Encoding header is usually sent when mod_deflate is enabled.

Date and Content-Length are not configurable as they are part of the HTTP spec. Date is included as a MUST (except under some conditions) and Content-Length as a SHOULD .

See also How to remove date header from apache? and How to disable the Content-Length response header with Apache? .

Answer 2

Yes Apache is setting those by default. By the way, if you only care about the headers, you should use

curl -I local.testsite

-I returns the headers only (HTTP HEAD request), such that even if you had content on the page you would only get the header.