Extend Wordpress Widget

extend_widget.php

<?php

class CustomExtentWidget
{
    function in_widget_form($widget, $return, $instance)
    {
        if (!in_array($widget->id_base, array('text'))) {
            return $instance;
        }
        if (!isset($instance['classes'])) $instance['classes'] = null;

        $fields = "<p>\n";

        // show dropdown
        $pages = get_pages();
        $fields .= "<label for='widget-{$widget->id_base}-{$widget->number}-classes'>" . apply_filters('widget_css_classes_class', esc_html__('Title Link to Page')) . ":</label>";
        $fields .= "<select name='widget-{$widget->id_base}[{$widget->number}][link_page]' id='widget-{$widget->id_base}-{$widget->number}-link_page'>";
        $fields .= "<option value=''>" . esc_attr__('Select') . "</option>";
        foreach ($pages as $page) {
            $selected = ($instance['link_page'] == $page->ID) ? 'selected="selected"' : '';
            $fields .= "<option value='" . $page->ID . "' " . $selected . ">" . $page->post_title . "</option>";
        }
        $fields .= "</select>";

        $fields .= "</p>";

        do_action('widget_css_classes_form', $fields, $instance);

        echo $fields;

        return $instance;
    }

    function widget_update_callback($instance, $new_instance)
    {
        $instance['link_page'] = $new_instance['link_page'];
        do_action('widget_css_classes_update', $instance, $new_instance);

        return $instance;
    }

    function widget_title($title)
    {
        $title = html_entity_decode($title);

        return $title;
    }

    function widget_display_callback($instance)
    {
        if (!empty($instance['title']) && !empty($instance['link_page'])) {
            $instance['title'] = '<a href="' . get_permalink($instance['link_page']) . '">' . $instance['title'] . '</a>';
        }

        return $instance;
    }
}

add_action('in_widget_form', array('CustomExtentWidget', 'in_widget_form'), 10, 3);
add_filter('widget_update_callback', array('CustomExtentWidget', 'widget_update_callback'), 10, 2);
add_filter('widget_title', array('CustomExtentWidget', 'widget_title'));
add_filter('widget_display_callback', array('CustomExtentWidget', 'widget_display_callback'));