Here is an example of a property handler using a closure that will later be evaluated.

property-handler-with-property-closure-example.php

<?php namespace Acme\Foo\Form;

class FooFormFields
{

        /**
         * Handle the form fields.
         */
        public function handle(FooFormBuilder $builder)
        {
                $builder->setFields(
                        [
                                'name',
                                [
                                        'field' => 'phone',
                                        'disabled' => function() use ($builder) {
                                                return $builder->getMode() === 'edit'; // Disable the input for edit forms.
                                        }
                                ]
                        ]
                );
        }
        
}