Variables, Data Types & Scopes

Data types

ColdFusion is dynamically typed. Variables are created on assignment and their type is inferred at runtime — no int, String, or var declarations required.

CFML's six core data types — dynamically inferred at runtime, no explicit type declarations needed.

Activity: Click the Terminal tab in your lab. Once the terminal is open, copy and paste the script below to create data_types.cfm and explore all six data types:

sudo tee /opt/coldfusion2025/cfusion/wwwroot/data_types.cfm << 'EOF'
<cfscript>
  // String
  myString = "Hello ColdFusion";
  writeOutput("<strong>String:</strong> " & myString & "<br>");

  // Numeric
  myInt  = 42;
  myFloat = 3.14;
  writeOutput("<strong>Numeric:</strong> " & myInt & " / " & myFloat & "<br>");

  // Boolean
  isActive = true;
  writeOutput("<strong>Boolean:</strong> " & isActive & "<br>");

  // Date
  today = now();
  writeOutput("<strong>Date:</strong> " & dateFormat(today, "yyyy-mm-dd") & "<br>");

  // Array
  fruits = ["apple", "banana", "cherry"];
  writeOutput("<strong>Array[1]:</strong> " & fruits[1] & "<br>");

  // Struct
  person = {name: "Alex", age: 30};
  writeOutput("<strong>Struct:</strong> " & person.name & " is " & person.age & "<br>");
</cfscript>
EOF

Open /data_types.cfm in the ColdFusion 2025 browser tab (right-click → Open Link in New Tab, then change the path). Or from the Terminal:

curl -s http://localhost:8500/data_types.cfm

All six data types rendered — each line shows the type name and its value.

Variable scopes

ColdFusion organises variables into named scopes. Every scope has a different lifetime and visibility.

The variables scope is the default when you omit a prefix. Always prefix session.* and application.* explicitly.

Scope lifetimes compared — request-scoped variables are cheapest; application-scoped variables persist for the life of the process.

Activity: Still in the Terminal tab, copy and paste the script below to create scopes.cfm and demonstrate the variables scope explicitly:

sudo tee /opt/coldfusion2025/cfusion/wwwroot/scopes.cfm << 'EOF'
<cfscript>
  // variables scope — explicit prefix
  variables.name    = "Alex";
  variables.course  = "ColdFusion 2025";

  writeOutput("<strong>variables.name:</strong> "   & variables.name   & "<br>");
  writeOutput("<strong>variables.course:</strong> " & variables.course & "<br>");

  // url scope — reads ?name= from the query string
  urlName = url.name ?: "no name passed";
  writeOutput("<strong>url.name:</strong> " & urlName & "<br>");
</cfscript>
EOF

Open /scopes.cfm in the browser to confirm the variables scope output:

curl -s http://localhost:8500/scopes.cfm

scopes.cfm with no query string — variables.* values are set, url.name falls back to the default.

Now verify that the variables. prefix is used explicitly in the file:

URL scope

Pass a query-string parameter and read it back with url.name:

curl -s "http://localhost:8500/scopes.cfm?name=TestUser"
# Expected: url.name: TestUser

Or in the browser, append ?name=TestUser to the URL:

https://<your-session-id>.iximiuz.com/scopes.cfm?name=TestUser

With ?name=TestUser appended, url.name resolves to TestUser instead of the default.

Scope resolution order

When you omit a scope prefix, CF walks this resolution chain top-to-bottom — always prefix to be explicit.

When you write just name without a prefix, ColdFusion checks scopes in this order:

1. local (inside a CFC function)
2. arguments
3. thread
4. query (inside a <cfloop query="...">)
5. variables
6. cgi, file, url, form, cookie, client

Always prefix to be explicit and avoid scope-bleed bugs. In a large application, an unqualified variable that accidentally resolves from url instead of variables can cause hard-to-trace security issues.

<cfdump var="#variables#" label="variables scope">
<cfdump var="#url#"       label="url scope">
<cfdump var="#session#"   label="session scope">

vi /opt/coldfusion2025/cfusion/wwwroot/scopes.cfm

When all the checks above are green, this lesson is complete. Your progress is saved automatically — move straight on to the next lesson.