# ParameterExists

Returns True if the specified parameter has been passed to the current template or has already been created during execution of the current template. Otherwise returns NO.

This function is provided for backward compatibility with previous versions of ColdFusion. You should use the function IsDefined instead.

See also GetClientVariablesList and IsDefined.

### Syntax

    ParameterExists(parameter)

##### parameter

Any syntactically valid parameter name.

### Example

    <!--- This example shows ParameterExists --->
    <HTML>
    <HEAD>
    <TITLE>
    ParameterExists Example
    </TITLE>
    </HEAD>

    <BODY BGCOLOR=silver>
    <H3>ParameterExists Example</H3>

    <CFIF ParameterExists(FORM.myString)>
    <P>Using ParameterExists, we have shown that the FORM
    field "myString" now exists.  However, this function is
    provided for backward compatibility and
    the function IsDefined should be used instead, as below.
    </CFIF>

    <CFIF IsDefined("FORM.myString")>
    <P>Because the variable FORM.myString has been defined, we
    can now show its contents.  This construction allows us
    to place a form and its resulting action template in the same
    template, while using IsDefined to control the
    flow of template execution.
    <P>The value of "FORM.myString" is
      <B><I><CFOUTPUT>#FORM.myString#</CFOUTPUT></I></B>
    <CFELSE>
    <P>During the first time through this template, the variable
    "FORM.myString" has not yet been defined, so we
    are not attempting to evaluate it.
    </CFIF>
    ...