Adobe Dreamweaver CC 2015 - Manual (Page 570)

563
Dynamic sites, pages and web forms
Last updated 6/3/2015
Session variables can only function if the user’s browser is configured to accept cookies. The server creates a session ID
number that uniquely identifies the user when the session is first initiated, then sends a cookie containing the ID
number to the user’s browser. When the user requests another page on the server, the server reads the cookie in the
browser to identify the user and to retrieve the user’s session variables stored in the server’s memory.
Collecting, storing, and retrieving information in session variables
Before creating a session variable, you must first obtain the information you want to store, and then send it to the server
for storage. You can gather and send information to the server using HTML forms or hypertext links containing URL
parameters. You can also obtain information from cookies stored on the user’s computer, from the HTTP headers sent
by the user’s browser with a page request, or from a database.
A typical example of storing URL parameters in session variables is a product catalog that uses hard-coded URL
parameters created using a link to send product information back to the server to be stored in a session variable. When
a user clicks the “Add to shopping cart” link, the product ID is stored in a session variable while the user continues to
shop. When the user proceeds to the check-out page, the product ID stored in the session variable is retrieved.
A form-based survey is a typical example of a page that stores form parameters in session variables. The form sends the
selected information back to the server, where an application page scores the survey and stores the responses in a
session variable to be passed to an application that might tally up the responses gathered from the survey population.
Or the information might be stored in a database for later use.
After information is sent to the server, you store the information in session variables by adding the appropriate code
for your server model to the page specified by the URL or form parameter. Referred to as the destination page, this page
is specified in either the action attribute of the HTML form or the href attribute of the hypertext link on the starting
page.
After you store a value in a session variable, you can use Dreamweaver to retrieve the value from session variables and
use it in a web application. After you define the session variable in Dreamweaver, you can insert its value in a page.
The HTML syntax for each appears as follows:
Both the server technology used and the method you use to obtain the information determines the code used to store
the information in a session variable. The basic syntax for each server technology is as follows:
ColdFusion
ASP
<% Session("variable_name") = value %>
The value expression is usually a server expression such as Request.Form(“lastname”). For example, if you use a URL
parameter called product (or an HTML form with the GET method and a text field called product) to gather
information, the following statements store the information in a session variable called prodID:
ColdFusion
ASP
<% Session("prodID") = Request.QueryString("product") %>
If you use an HTML form with the post method and a text field called txtProduct to gather the information, then the
following statements store the information in the session variable: