As with any programming tool, you cannot use just any word or name for ColdFusion variables, UDFs and custom tags. You must avoid using any name that can be confused with a ColdFusion element. In some cases, if you use a word that ColdFusion uses--for example, a built-in structure name--you can overwrite the ColdFusion data.

The following list indicates words you must not use for ColdFusion variables, user-defined function names, or custom tag names. While some of these words can be used safely in some situations, you can prevent errors by avoiding them entirely. For a complete list of reserved words, see the CFML Reference.

• Built-in function names, such as Now or Hash
• Scope names, such as Form or Session
• Any name starting with cf. However, when you call a CFML custom tag directly, you prefix the custom tag page name with cf_.
• Operators, such as NE or IS
• The names of any built-in data structures, such as Error or File
• The names of any built-in variables, such as RecordCount or CGI variable names
• CFScript language element names such as for, default, or continue

You must also not create form field names ending in any of the following, except to specify a form field validation rule using a hidden form field name. (For more information on form field validation, see Introduction to Retrieving and Formatting Data.)

• _integer
• _float
• _range
• _date
• _time
• _eurodate

Because ColdFusion is not case-sensitive, all of the following are reserved words: IS, Is, iS, and is.