This can help,
http://book.cakephp.org/view/189/Automagic-Form-Elements#options-before-options-between-options-separator-a-191
To enter the type of radio signal, the 'separator' attribute can be used to enter markup to separate each input / label pair.
Code view
<?php echo $form->input('field', array( 'before' => '--before--', 'after' => '--after--', 'between' => '--between---', 'separator' => '--separator--', 'options' => array('1', '2'), 'type' => 'radio' ));?>
Conclusion:
<div class="input"> --before-- <input name="data[User][field]" type="radio" value="1" id="UserField1" /> <label for="UserField1">1</label> --separator-- <input name="data[User][field]" type="radio" value="2" id="UserField2" /> <label for="UserField2">2</label> --between--- --after-- </div>
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