ColdFusion Variable Types

ColdFusion variables come in many different types. Firstly, all variables belong to a scope. There are many different scopes and each variable created in your application belongs to one of these scopes. Secondly, all variables can be either local or global. Thirdly, all variables are either persistent or non-persistent.

Variable Scopes

A variable's scope is determined by its origin. The scope determines a number of properties about the variable, such as its life span, timeout, and storage location, and therefore, how it can be used.

Below is a list of the available scopes for ColdFusion variables:

"Scoping" your Variables

When you set or read a variable, it is good practice to tell ColdFusion which scope it belongs to. Although this is not required, it will avoid any confusion around whether the correct variable is being used or not. You may occasionally encounter two or more variables with the same name, but belonging to a different scope. To avoid the wrong one being used, you should scope your variables.

You scope a variable simply by prefixing the variable name with the name of the scope (and separating them with a dot).

<cfset scope.variablename="value">
<cfoutput>
  #scope.variablename#
</cfoutput>

For example, to scope a session variable, you would do something like this:

<cfset Session.BodyType = "Perfect">
<cfoutput>
  Body Type: #Session.BodyType#
</cfoutput>

Variable Persistence

The following chart outlines the different variable scopes, whether they're local or global, and indicates whether they are persistent variables or non-persistent.

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