<?php class WP_Customize_Multiple_Checkbox_Control extends WP_Customize_Control {
    public $type = 'multiple_checkbox';
    
    public function render_content() {
        if (empty($this->choices)) {
            return;
        }
        ?>
        <span class="customize-control-title"><?php echo esc_html($this->label); ?></span>
        <?php if ($this->description) : ?>
            <span class="description customize-control-description">
                <?php echo esc_html($this->description); ?>
            </span>
        <?php endif; ?>
        
        <?php foreach ($this->choices as $key => $label) : ?>
            <label>
                <input type="checkbox" 
                       value="<?php echo esc_attr($key); ?>" 
                       <?php checked(is_array($this->value()) && in_array($key, $this->value())); ?> 
                       <?php $this->link(); ?> />
                <?php echo esc_html($label); ?>
            </label><br>
        <?php endforeach; ?>
        <?php
    }
}
