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A group of radio buttons is identified by the common
name attribute. Out of a group of buttons, only one can be selected (or none).When submitting a form to the
server, the value attribute of the selected radio buttons
is transmitted to the server.Therefore, it is quite messy
but rather trivial to prefill a group of radio buttons:
Just compare the value in $_GET/$_POST with the associated
value. If it fits, print out checked, the HTML
attribute that preselects a radio button, as shown in
the code.
This code can be extended so that a radio button
is preselected when the user has previously saved
his selection in a cookie, using the include file
getFormData.inc.php, as shown in the following code.
Although some websites pretend to group check boxes
like radio buttons, this is technically not true. Every
check box stands on its own; therefore, they all should
have different names (it would not make sense to give them identical names).Then each check box can be
treated individually: Check for the associated value
attribute and print out the checked HTML attribute, if
there is a match.
When using cookie data (if available), the code changes slightly.
On a single selection list, the value of the selected <option> element is transferred to the server when submitting the form.This value can then be manually checked to prefill the form, using the selected HTML attribute, as shown in the code.
The same effect can be implemented using getFormData.inc.php; then data from the site’s cookies is used, if available.
Next week, we begin with a look at Preselecting MultipleSelection Lists, Processing Graphical Submit Buttons, Checking Mandatory Fields and more.
Excerpted from Chapter 4: Interact with Web Forms from the PHP Phrasebook by Christian Wenz. ISBN 0672328178, Copyright © 2005. Used with the permission of Sams Publishing.
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Created: March 27, 2003
Revised: January 16, 2006
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