Being a dynamic application development tool, CFML includes
the feature of a programming language like variables, constants, functions,
loops (flow-control tags), etc. CFML also includes CFScript which allows us to
included cover a large range of functionalities like creating forms,
manipulating variables, processing ColdFusion pages, accessing database,
handling errors, manipulating files and directories, using protocols, etc. One
can also create his own custom tags which can encapsulate frequently used code
at one place. If custom tags are written using CFML, then they can take the
advantage of all the built-in tags and even other custom tags of ColdFusion.
CFX tags are custom tags written in a programming language like Java or C++.
Generally, CFX tags are executed faster than CFML custom tags since they are
compiled. Similarly, for functions, the built-in functions in ColdFusion can
perform a large range of functionalities including creating queries and
manipulating them, evaluating the values of dynamic data, performing
mathematical operations, etc. One can also create user-defined functions using ColdFusion.
ColdFusion components are basically a group of related user-defined functions
and variables. They also have the capability of providing and controlling the
access to the component's content. ColdFusion components can provide web
services and also make them available on the Internet. They can also provide ColdFusion
services that Flash clients can call directly.
Now, coming down to variables and constants, constants are
simple scalar values whose value does not change during program execution.
Variables' value can be set and reset. The two main characteristic of a
variable is its scope and its data type. Some examples for the scope of a
variable are the following.
Variables scope (local) – It is the default scope whenever we
declare a variable using the cfset and cfparam tags. Such types of variables
are only available on the page on which they are declared.
Form – These variables are the form variables which are sent to
the form’s action page on submission of the form.
URL – The parameters passed in the URL to call the current page.
Request – These variables are available to all pages. These are
used to hold the information that is required for the duration of a HTTP
CGI – These variables are environment variables identifying the
context in which the page was requested.
Cookie – These are the variables present in the user’s browsers
Client – These variables are associated with one client.
Session – These variables are associated with one session. These
are available for the time for which the client maintains a session.
Application - These variables are associated with one application
on the server.
Server - These variables are associated with one ColdFusion
Arguments – These are the variables passed which call a
Similarly, for the data type of a variable, it can be:
Simple, representing one value. For example, strings, integers,
Boolean values, etc.
Complex, like arrays, structures, etc.
Binary, representing raw data like the content of a GIF file.
Object, like Java, web services, ColdFusion components objects,
ColdFusion includes a lot of flow control tags like cfif,
cfelse, cfelseif, cfswitch, cfcase, cfdefaultcase, cfloop, cfbreak, efexit,
etc. cfif, cfelse and cfelse provide the functionality of if-then-else
conditional processing. If a condition is true, then execute a block of code
and if not, then execute the block of code in cfelse part. If multiple
conditions are given, check for each condition and whichever condition
satisfies, execute the block of code for that condition. Similarly, cfswitch,
cfcase and cfdefaultcase allow for selecting from a set of different codes
depending on the value of an expression. The cfloop tag allows looping over a
block of code for a desired number of times. cfbreak tag is used to exit the
CFScript tag in ColdFusion is used to write code in
programming language similar to Java, but is simpler than Java. It provides an
efficient way to write ColdFusion logic.