Problem with php 7.x

Hi,

i upgrated the php version of my site to 7.0.25 but i have these error with your plugin:

Warning: Declaration of shailan_PageWalker::start_lvl(&$output, $depth) should be compatible with Walker::start_lvl(&$output, $depth = 0, $args = Array) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-page-walker.php on line 111

Warning: Declaration of shailan_PageWalker::end_lvl(&$output, $depth) should be compatible with Walker::end_lvl(&$output, $depth = 0, $args = Array) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-page-walker.php on line 111

Warning: Declaration of shailan_PageWalker::start_el(&$output, $page, $depth, $args = Array, $current_page = NULL) should be compatible with Walker::start_el(&$output, $object, $depth = 0, $args = Array, $current_object_id = 0) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-page-walker.php on line 111

Warning: Declaration of shailan_PageWalker::end_el(&$output, $page, $depth) should be compatible with Walker::end_el(&$output, $object, $depth = 0, $args = Array) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-page-walker.php on line 111

Warning: Declaration of shailan_CategoryWalker::start_lvl(&$output, $depth, $args) should be compatible with Walker::start_lvl(&$output, $depth = 0, $args = Array) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-category-walker.php on line 154

Warning: Declaration of shailan_CategoryWalker::end_lvl(&$output, $depth, $args) should be compatible with Walker::end_lvl(&$output, $depth = 0, $args = Array) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-category-walker.php on line 154

Warning: Declaration of shailan_CategoryWalker::start_el(&$output, $category, $depth, $args) should be compatible with Walker::start_el(&$output, $object, $depth = 0, $args = Array, $current_object_id = 0) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-category-walker.php on line 154

Warning: Declaration of shailan_CategoryWalker::end_el(&$output, $page, $depth, $args) should be compatible with Walker::end_el(&$output, $object, $depth = 0, $args = Array) in /web/htdocs/www.ponzaracconta.it/home/wp-content/plugins/dropdown-menu-widget/shailan-category-walker.php on line 154

Now i returned to php 5.6.32 and it works.

Thank you for support