Tutorial 13: Giving Form to Forms
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Hidden controls
Hidden controls are not displayed and cannot be manipulated by the user, nor can their value be changed. They are used to supply a fixed name/value pair along with the rest of the form. This could be useful if the program that processes the submission does a number of things, but you want the specific form to do only a subset of these. Hidden controls have a TYPE of hidden. For instance, a program that subscribes and unsubscribes people from a mailing list might have a field called action that could have the value subscribe or unsubscribe, and you want to make a form that only allows unsubscribtion. You could do this with something like:
<FORM METHOD="POST" ACTION="/cgi-bin/html/formdump.cgi" ENCTYPE="multipart/form-data"> <P>To unsubscribe, enter your e-mail address: <INPUT TYPE="text" NAME="email" SIZE="30"> <INPUT TYPE="submit" VALUE="Submit"> <INPUT TYPE="hidden" NAME="action" VALUE="unsubscribe"> </FORM>
A form that offers the user a choice instead could be something like this:
<FORM ACTION="/cgi-bin/html/formdump.cgi" METHOD="GET" ENCTYPE="application/x-www-form-urlencoded"> <P>Enter your e-mail address: <INPUT TYPE="text" NAME="email" SIZE="30"> <P>Subscribe <INPUT TYPE="radio" NAME="action" VALUE="subscribe"> Unsubscribe <INPUT TYPE="radio" NAME="action" VALUE="unsubscribe" CHECKED> <INPUT TYPE="submit"> </FORM>
