Sindbad~EG File Manager

<?php

function realpro_mailchimp_add_params($params) {
    global $wp_registered_widgets;

    $widget_id = $params[0]['widget_id'];
    $widget_obj = $wp_registered_widgets[$widget_id];
	$widget_instance = get_option('widget_mc4wp_form_widget');
	$num = substr($widget_id, -1);

    if ($widget_obj['callback'][0]->id_base === 'mc4wp_form_widget') { 
        $sub_title = '<p class="sub-title">'. esc_html__($widget_instance[$num]['sub_title'], 'realpro' ) .'</p>';

		if($sub_title) {
			$params[0]['after_title'] .= $sub_title;
		}
    }
    return $params;
}

add_filter('dynamic_sidebar_params', 'realpro_mailchimp_add_params');

function realpro_mailchimp_widget_field($instance, $widget) {
    $sub_title = isset($instance['sub_title']) ? sanitize_text_field($instance['sub_title']) : ''; 
    ?>
    <p>
        <label for="<?php echo esc_attr($widget->get_field_id('sub_title')); ?>">
            <?php echo esc_html__('Sub Title:', 'realpro'); ?>
        </label>
        <input class="widefat" id="<?php echo esc_attr($widget->get_field_id('sub_title')); ?>" name="<?php echo esc_attr($widget->get_field_name('sub_title')); ?>" type="text" value="<?php echo esc_attr($sub_title); ?>" />
    </p>
    <?php
}

add_action('mc4wp_form_widget_form', 'realpro_mailchimp_widget_field', 10, 2);

function realpro_mailchimp_widget_update_settings($new_settings, $old_settings, $widget) {
    $new_settings['sub_title'] = isset($new_settings['sub_title']) ? sanitize_text_field($new_settings['sub_title']) : '';

    return $new_settings;
}
add_filter('mc4wp_form_widget_update_settings', 'realpro_mailchimp_widget_update_settings', 10, 3);