PHP Cookbook

11.6. Debugging the Raw HTTP Exchange

Problem

You want to analyze the HTTP request a browser makes to your server and the corresponding HTTP response. For example, your server doesn’t supply the expected response to a particular request so you want to see exactly what the components of the request are.

Solution

For simple requests, connect to the web server with telnet and type in the request headers:

% telnet www.example.com 80
Trying 10.1.1.1...
Connected to www.example.com.
Escape character is '^]'.
GET / HTTP/1.0
               Host: www.example.com

HTTP/1.1 200 OK
Date: Sat, 17 Aug 2002 06:10:19 GMT
Server: Apache/1.3.26 (Unix) PHP/4.2.2 mod_ssl/2.8.9 OpenSSL/0.9.6d
X-Powered-By: PHP/4.2.2
Connection: close
Content-Type: text/html

// ... the page body ...

Discussion

When you type in request headers, the web server doesn’t know that it’s just you typing and not a web browser submitting a request. However, some web servers have timeouts on how long they’ll wait for a request, so it can be useful to pretype the request and then just paste it into telnet. The first line of the request contains the request method (GET ), a space and the path of the file you want (/), and then a space and the protocol you’re using (HTTP/1.0). The next line, the Host header, tells the server which virtual host to use if many are sharing the same IP address. A blank line tells the server that the request is over; it then spits back its response: first headers, then a blank line, and then the body of the response. ...