在WordPress 4.4最新更新之前，我能够通过以下方式从多选菜单在小部件中创建阵列实例：

<?php $cats = get_categories(); ?>  
<select multiple="multiple" name="<?php echo $this->get_field_name(\'cats][\') ?>">
    <?php foreach ( $cats as $cat ) { ?>
        <option value="<?php echo $cat->term_id ?>"><?php echo $cat->name; ?></option>
    <?php } ?>
</select>

发生了什么变化，我如何解决？

=======

更新：小部件的完整代码：

###################################################################

function widet_sample() {
    register_widget(\'widet_sample\');
}
add_action(\'widgets_init\', \'widet_sample\');

class widet_sample extends WP_Widget {

    function widet_sample() {
        parent::__construct(false, \'SAMPLE\');
    }

    function update($new_instance, $old_instance) {
        $instance = $old_instance;
        $instance[\'cats\'] = $new_instance[\'cats\'];
        return $instance;
    }

    function form($instance) {
?>
<p>
    Categories IDs: <?php print_r($instance[\'cats\']); ?>
</p>
<p>
    <?php $cats = get_categories(); ?>  
    <select class="widefat" multiple="multiple" name="<?php echo $this->get_field_name(\'cats][\') ?>">
        <?php foreach ( $cats as $cat ) { ?>
            <option value="<?php echo $cat->term_id ?>"><?php echo $cat->name; ?></option>
        <?php } ?>
    </select>
</p>    
<?php
    }
}

###################################################################