<?php

// Add "completed" field
$this->add(array(
    'type' => 'checkbox',
    'name' => 'completed',
    'attributes' => [
        'id' => 'completed',
    ],
    'options' => array(
        'label' => 'Completed',
         // 'use_hidden_element' => true,
         'checked_value' => '1',
         'unchecked_value' => '0'
     )
));// Add input filter for the "completed" field
$inputFilter->add([
    'name'     => 'completed',
    'required' => true,
    'validators' => [
        [
            'name' => 'Digits',
        ]
    ],
]);