CGI Encoding Scheme

Form data consists of a list of name/value pairs. Before transmitting this data to the server and the CGI program, the browser encodes the information using a scheme called URL encoding (specified by the MIME type application/x-www-form-urlencode). The encoding scheme consists of the following:

* URL encoding certain non-alphanumeric characters. This process consists of replacing these characters with a percent sign followed by the hexadecimal value of the character. Some of these characters and their corresponding hexadecimal values are here:
Chracter Hexadecimal Value
Tab 09
Space 20
" 22
( 28
) 29
, 2C
; 3B
@ 40
* Replacing spaces with the plus sign (+).
* Separating each name and value with an equal sign (=).
* Separating each name/value pair with an ampersand (&).

For example, suppose you have the following name/value pairs:

name Zhanshou Yu
major Computer Science
e-mail zyu@bayou.uh.edu

In order to encode these pairs, first replace the non-alphanumeric characters. In this example, only one charater exists,@, which is replaced with %40. So we have:

name Zhanshou Yu
major Computer Science
e-mail zyu%40bayou.uh.edu

Now, replace all spaces with a plus sign. We get:

name Zhanshou+Yu
major Computer+Science
e-mail zyu%40bayou.uh.edu

Seperate each name and value with an equal sign:

name=Zhanshou+Yu
major=Computer+Science
e-mail=zyu%40bayou.uh.edu

Finally, separate each pair with an ampersand (&):

name=Zhanshou+Yu&major=Computer+Science&email=zyu%40bayou.uh.edu

The CONTENT_LENGTH is equal to the number of character in the coding string. This example has 64 characters, so the CONTENT_LENGTH is 64.