Adobe Dreamweaver CC 2014 v.13 - Manual (Page 634)

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Form parameters store retrieved information that is included in the HTTP request for a web page. If you create a form that uses the POST method,
the data submitted by the form is passed to the server. Before you begin, make sure you pass a form parameter to the server.
About session variables
Session variables let you store and display information maintained for the duration of a user’s visit (or session). The server creates a different
session object for each user and maintains it for a set period of time or until the object is explicitly terminated.
Because session variables last throughout the user’s session and persist when the user moves from page to page within the website, they’re ideal
for storing user preferences. Session variables can also be used for inserting a value in the page’s HTML code, assigning a value to a local
variable, or providing a value to evaluate a conditional expression.
Before defining session variables for a page, you must create them in the source code. After you create a session variable in the web application’s
source code, you can use Dreamweaver to retrieve its value and use it in a web page.
How session variables work
Session variables store information (usually form or URL parameters submitted by users) and make it available to all of a web application’s pages
for the duration of the user’s visit. For example, when users log on to a web portal that provides access to e-mail, stock quotes, weather reports,
and daily news, the web application stores the login information in a session variable that identifies the user throughout the site’s pages. This
allows the user to see only the types of content they have selected as they navigate through the site. Session variables can also provide a safety
mechanism by terminating the user’s session if the account remains inactive for a certain period of time. This also frees server memory and
processing resources if the user forgets to log off a website.
Session variables store information for the life of the use session. The session begins when the user opens a page within the application and ends
when the user does not open another page in the application for a certain period of time, or when the user explicitly terminates the session
(typically by clicking a “log-off” link). While it exists, the session is specific to an individual user, and every user has a separate session.
Use session variables to store information that every page in a web application can access. The information can be as diverse as the user’s name,
preferred font size, or a flag indicating whether the user has successfully logged in. Another common use of session variables is to keep a running
tally, such as the number of questions answered correctly so far in an online quiz, or the products the user selected so far from an online catalog.
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
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