Checkbox problem

<?php

error_reporting(E_ALL);
ini_set("display_errors", 1);

/*
    Plugin Name: Image Gallery Uploader
    Plugin URI: https://github.com/kschat
    Description: This plugin allows visitors of your WordPress site to upload images to a gallery.
    Version: 0.1
    License: GPL2

include_once 'Debug.php';

define('PLUGIN_PATH', plugin_dir_url(__FILE__));

class UploaderWidget extends WP_Widget {

    // Constructor
    function __construct() {
        $widget_ops = array(
        'classname' => 'image-uploader',
        'description' => 'A widget used to upload photos to a gallery.');

        $control_ops = array('width'=> '200', 'height'=> '350', 'id_base' => 'image-uploader-id');

        parent::__construct('image-uploader-id', 'Uploader Widget', $widget_ops, $control_ops);
    }

    function widget($args, $instance) {
        extract($args);

        $title = apply_filters('widget_title', $instance['title']);

        echo $before_widget;

        if($title) {
            echo $before_title . $title . $after_title;
        }
        ?>
        <img src="<?php echo PLUGIN_PATH;?>images/defaultImage.gif"><br />
        <p>
        <label for="upload-button" style="color:black;">Upload new Image:</label>
        <input type="file" name="upload-button" />
        </p>
        <?php

        echo $after_widget;
    }

    function update($new_instance, $old_instance) {
        $instance = $old_instance;

        $instance['title'] = $new_instance['title'];
        $instance['imgDir'] = $new_instance['imgDir'];
        //$instance['categories'][0]['selected'] = 1;
        //$instance['categories'][0]['label'] = '';
        //$instance['newCategory'] = '';



        $instance['categories'] = $this->parseAndCombineCategories((get_option('UploaderWidget_categories')), $new_instance['newCategory']);

        for($i=0; $i<sizeof($instance['categories']); $i++) {
            $instance['categories'][$i]['selected'] = (int)$new_instance['categories'][$i]['selected'];
        }

        //$instance['categories'][0]['selected'] = 1;
        //$instance['categories'][0]['label'] = 'label';

        update_option('UploaderWidget_categories', $instance['categories']);

        return $instance;
    }

    function form($instance) {
        $defaults = array('title'       => 'Uploader Widget',
                          'imgDir'      => PLUGIN_PATH.'images/',
                          'categories'  => array(0 => array('selected'   => 0,
                                                            'label'      => 'option1'),
                                                 1 => array('selected'   => 0,
                                                            'label'      => 'option2'),
                                                 2 => array('selected'   => 0,
                                                            'label'      => 'option3')));

        $instance = wp_parse_args((array)$instance, $defaults);
        //$instance['categories'] = null;
        //$instance['newCategory'] = null;
        ?>
        <p>
            <label for="<?php echo $this->get_field_id('title');?>">Title:</label><br />
            <input type= "text" id="<?php echo $this->get_field_id('title');?>" name="<?php echo $this->get_field_name('title');?>"
                   value="<?php echo $instance['title'];?>" />
        </p>

        <p>
            <label for="<?php echo $this->get_field_id('imgDir');?>">Saved Images Directory:</label>
            <input type="text" id="<?php echo $this->get_field_id('imgDir');?>" name="<?php echo $this->get_field_name('imgDir');?>"
                    value="<?php echo $instance['imgDir'];?>" readonly="readonly" />
            <input type="file" />
        </p>

        <p>
            Categories:<br />
            <?php
            $this->displayCategories($instance['categories']);
            $this->displayNewCategoriesInput('newCategory');
            ?>
        </p>
        <?php
    }

    function parseAndCombineCategories($categories, $newCategories) {
        //unset($categories);
        if(trim($newCategories) != "") {
            unset($categories['NoCategories']);
            $newCategories = split(',', $newCategories);
            $newSize = sizeof($categories) + sizeof($newCategories);
            $oldSize = sizeof($categories);

            for($i=sizeof($categories); $i<$newSize; $i++) {
                $categories[$i]['selected'] = 0;
                $categories[$i]['label'] = $newCategories[$i - $oldSize];
            }
        }
        else if(empty($categories)) {
            return $categories = array('NoCategories' => '<b>No categories have been made yet.</b>');
        }
        return (array)$categories;
    }

    function displayCategories($categories) {
        if(array_key_exists('NoCategories', $categories)) {
            ?> <p> <?php
            echo $categories['NoCategories'];
            ?> </p> <?php
            return;
        }
        ?> <table class="form-table" id="image-gallery-form-table"> <?php
        for($i=0; $i<sizeof($categories); $i++) {
            echo ($i % 2 == 0) ? "<tr><td>": "<td>"; ?>
            <input class="checkboxes" type="checkbox" <?php checked((int)$categories[$i]['selected'], 1); ?> id="<?php echo $this->get_field_id($categories[$i]['label']); ?>"
                   name="<?php echo $this->get_field_name($categories[$i]['label']);?>" />
                <label for="<?php echo $this->get_field_id($categories[$i]['label']); ?>"><?php echo $categories[$i]['label']; ?></label>
                <?php echo ($i % 2 == 0) ? "</td>": "</td></tr>";
        }
        ?> </table> <?php echo Debug::printArray($categories, false);
    }

    function displayNewCategoriesInput($field) {
        ?>
        <label for="<?php echo $this->get_field_id($field); ?>">Add a new category
            (seperate names with a ',' to add multiple categories):</label>
            <input type="text" name="<?php echo $this->get_field_name($field); ?>"
                   id="<?php echo $this->get_field_id($field); ?>" />
        <?php
    }
}

function registerUploaderWidget() {
    register_widget('UploaderWidget');
}

add_action('widgets_init', 'registerUploaderWidget');
?>