Adobe 38043740 - ColdFusion Standard - Mac Development Manual page 984

DEVELOPING COLDFUSION 9 APPLICATIONS
Working with Documents, Charts, and Reports
Using CAPTCHA to verify membership
The following example shows how to create a simple form to verify whether a person (rather than a computer
generating spam) is registering to receive an online newsletter. You generate the CAPTCHA image from a random text
string on the form page and verify the response on the action page.
Example
Enter the following code on the form page:
<!--- Set the length of the text string for the CAPTCHA image. --->
<cfset stringLength=6>
<!--- Specify the list of characters used for the random text string. The following list
limits the confusion between upper- and lowercase letters as well as between numbers and
letters. --->
<cfset
stringList="2,3,4,5,6,7,8,9,a,b,d,e,f,g,h,j,n,q,r,t,y,A,B,C,D,E,F,G,H,K,L,M,N,P,Q,R,S,
T,U,V,W,X,Y,Z">
<cfset rndString="">
<!--- Create a loop that builds the string from the random characters. --->
<cfloop from="1" to="#stringLength#" index="i">
<cfset rndNum=RandRange(1,listLen(stringList))>
<cfset rndString=rndString & listGetAt(stringList,rndNum)>
</cfloop>
<!--- Hash the random string. --->
<cfset rndHash=Hash(rndString)>
<!--- Create the user entry form. --->
<cfform action="captcha2.cfm" method="post">
<p>Please enter your first name:</p>
<cfinput type="text" name="firstName" required="yes">
<p>Please enter your last name:</p>
<cfinput type="text" name="lastName" required="yes">
<p>Please enter your e-mail address:</p>
<cfinput type="text" name="mailTo" required="yes" validate="email">
<!--- Use the randomly generated text string for the CAPTCHA image. --->
<p><cfimage action="captcha" fontSize="24" fonts="Times New Roman" width="200" height="50"
text="#rndString#"></p>
<p>Please type what you see: </p>
<p><cfinput type="text" name="userInput" required="yes" maxlength=6>
<cfinput type="hidden" name="hashVal" value="#rndHash#">
<p><cfinput type="Submit" name ="OK" value="OK"></p>
</cfform>
Enter the following code on the action page:
Last updated 1/20/2012
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