Im trying to replace my template's primary menu through a plugin so that I don't have to make changes to the header.php.
I found this code in another question answered here in 2011 (Replacing WordPress menu functionality with a plugin)
add_filter('wp_nav_menu', 'my_menu_func');
function my_menu_func(){
print "Testing 123";
}
It worked but it replaced both my top primary menu and the widget side menu.
How can I specify which menu to target when using the filter?