WordPress local install with XAMPP

Strict Standards: Declaration of My_Walker::start_el() should be compatible with Walker_Nav_Menu::start_el(&$output, $item, $depth = 0, $args = Array, $id = 0) in C:\xampp\htdocs\Myonlineschool\wp-content\themes\sliding-door\functions.php on line 294

Strict Standards: Declaration of My_Walker::end_el() should be compatible with Walker_Nav_Menu::end_el(&$output, $item, $depth = 0, $args = Array) in C:\xampp\htdocs\Myonlineschool\wp-content\themes\sliding-door\functions.php on line 294

Errors after configuring Multiste.

Added – define(‘WP_DEBUG’, true);

define(‘WP_ALLOW_MULTISITE’, true);

define(‘MULTISITE’, true);
define(‘SUBDOMAIN_INSTALL’, false);
define(‘DOMAIN_CURRENT_SITE’, ‘localhost’);
define(‘PATH_CURRENT_SITE’, ‘/’);
define(‘SITE_ID_CURRENT_SITE’, 1);
define(‘BLOG_ID_CURRENT_SITE’, 1);

to wp-config.php file.

.htaccess file.

# BEGIN WordPress

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ – [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

# END WordPress

I cannot see where I have gone wrong.