Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

Chapter

ne of the main motivations for building Web pages dynamically is so

that the result can be based upon user input. This chapter shows you

O

how to access that input.

3.1 The Role of Form Data

If you've ever used a search engine, visited an on line bookstore,

tracked stocks on the Web, or asked a Web based site for quotes on

plane tickets, you've probably seen funny looking URLs like

http://host/path?user=Marty+Hall&origin=bwi&dest=lax

. The

part after the question mark (i.e., 

user=Marty+Hall&origin=

bwi&dest=lax

) is known as form data (or query data) and is the most com 

mon way to get information from a Web page to a server side program.

Form data can be attached to the end of the URL after a question mark (as

above), for 

GET

 requests, or sent to the server on a separate line, for 

POST

requests. If you're not familiar with HTML forms, Chapter 16 (Using

HTML Forms) gives details on how to build forms that collect and transmit

data of this sort.

Extracting the needed information from this form data is traditionally one

of the most tedious parts of CGI programming. First of all, you have to read

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