To create an <option value="custom_value"> tag with custom values in cakephp, you just have to assign an associative array to option attribute of select tag like below example.
<?php
$item_list = array('7'=>'mouse','10'=>'keyboard','11'=>'video card');
//cakephp way of creating select tag
...
echo $form->input('sel1', array(
'type'=>'select',
'options'=>array($item_list),
'label'=>'Item',
'empty'=>'Select item...',)
);
?>
It will generate below html tag
