PHP —

HTTP Responses

When a web server processes a request from a browser, it attempts to apply the method to the identified resource and create a response. The action of the request may succeed, or it may fail for a variety of reasons, but the web server always sends a response message back to the browser.

A HTTP response message contains a status line, header fields, and the requested entity as the body of the message. The body of the response is usually the resource requested in the request message. Example B-3 shows the result of a GET method on a small HTML file.

Example B-3. An example HTTP response message
HTTP/1.1 200 OK
Date: Tue, 24 Oct 2001 02:54:37 GMT
Server: Apache/1.3.19
Last-Modified: Tue, 24 Oct 2001 02:53:08 GMT
ETag: "4445f-bf-39f4f994"
Content-Length: 321
Accept-Ranges: bytes
Connection: close
Content-Type: text/html
<!DOCTYPE HTML PUBLIC
   "-//W3C//DTD HTML 4.0 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd" >
<html>
<head><title>Grapes and Glass</title></head>
<body>
<img src="http://example.com/grapes.gif">
<p>Welcome to my simple page
<p><img src="http://example.com/glass.gif">
</body>
</html>

The status line-the first line of the message-starts with the protocol version of the message, followed by a status code and a reason phrase, each separated by a space character. The status line is followed by the header fields. As with the request, each field is represented as a name and value pair separated with a colon character. A blank line separates the header fields and the body of the response.