• Creating Variables
• Kinds of Variables
• Client Variables
• Server Variables
• Session Variables

Creating Variables

The basic HTML pages usually begin and end with a tag. Even ColdFusion the pages begin and end with a tag. As variables in other languages, the ColdFusion variable is assigned a value. In ColdFusion applications, the variables are used in many different ways. In a simple way the variables, which are used in ColdFusion forms, are to hold data submitted in an application. Variables are essential for each field in a form to handle the form inputs.   Each set of beginning and end tags always has the same name but the end tag name is preceded by a slash (/).  ColdFusion code displays the dynamic information such as date but in case of HTML the dynamic information such as date cannot be displayed.

Kinds of Variables

Local:               Variables created with the CFSET tag or CFPARAM tag in a template

URL:                Variables reflecting parameters appended to a URL

CGI:                 Variables reflecting the CGI environment variables of the context of the requested template.      

Cookie:            Variables reflecting cookies passed to the template by the requesting browser. (CFCOOKIE tag is used)

Query:              Variables reflecting the results of a query.

Form:               Variables reflecting the values of the fields in a form submitted to the current template

Client:               Validation used to associate data with a specific client.

Server:             Validation used to associate data with a specific Web Server.

Session:            Validation used to associate data with a specific client Session.

Application:      Validation used to associate data with a specific ColdFusion Application.

Client Variables

Client Variables keep track of users as they move through the pages.  A client record is created for each browser that requests a page in an application in which client state management is enabled. CFID and CFTOKEN identify the client’s unique record, which is stored in an HTTP cookie in the user’s browser.  Within the client record the application define the variables. These client variables are accessible as parameters in every page, which is requested by the client.

To Create client variables CFAPPLICATION tag is used as

<CFAPPLICATION Name = “myappl”

            ClientManagement=”yes”>

This statement is written in the .cfm file.

Server Variables

The Server Variables are always tied with single Web server and can be accessed by all clients and application on that server.  The Server variable is stored in the server’s RAM until the server has been stopped. The server variable is lost only when the server is shutdown.  The server variable is used when you want to create a client variable that can be accessed by any client connecting to the server.

Session Variables

The Session Variables are associated with a single client. Timeout period is specified and are stored in the server’s RAM.  The default timeout period is 20 minutes, which is set in CF Administrator. The session variables are used for short period. Once the variables are expired, each time the user returns using the same client, their session variables must be re-established.  It is better to keep the expiration date for session variables to a minimum since the server’s RAM limits them.

List of Tags

Form Tags

DATABASE MANIPULATION TAGS

DATA OUTPUT TAGS

EXCEPTION HANDLING TAGS

EXTENSIBILITY TAGS

FILE MANAGEMENT TAGS

FLOW-CONTROL TAGS

INTERNET PROTOCOL TAGS

JAVA SERVLET AND JAVA OBJECT TAGS

PAGE PROCESSING TAGS

VARIABLE MANIPULATION TAGS

WEB APPLICATION FRAMEWORK TAGS

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