When a browser makes a request to a server, the web server and the browser create environment variables. In ColdFusion, these variables are referred to as CGI environment variables. CGI Environment variables contain data about the transaction between the browser and the server, such as the IP Address, browser type, and authenticated username. The available CGI variables depend on the browser and server software.
The CGI variables are available to ColdFusion pages in the CGI scope. They take the CGI prefix regardless of whether the server uses a server API or CGI to communicate with the ColdFusion server. You can reference CGI environment variables for a given page request anywhere in the page. CGI variables are read-only.
By default, when you use the cfdump tag to display the CGI scope, or when you request debug output of the CGI scope, ColdFusion attempts to display a fixed list of standard CGI environment variables. Because the available variables depend on the server, browser, and the types of interactions between the two, not all variables are normally available. They are represented by empty strings in the debug output. You can request any CGI variable in your application code, including variables that are not in the list variables displayed by dump and debug output.
ColdFusion checks for the following variables for the cfdump tag and debug output:
The following sections describe how to test for CGI environment variables and provide information on some of the more commonly used CGI environment variables