add_menu_page() with variable function

Question

How can I use add_menu_page() functions some variable function ?

add_menu_page('My page','My page','manage_options','my_page', 'func' );

$func = function() {
        echo "Done !";
};

I know I can use like

function func() {
            echo "Done !";
};

But how can I use like

$func = function() {
            echo "Done !";
};

to call it ?

Answer 1

You have to declare the closure before you call add_menu_page():

$func = function() {
            echo "Done !";
};

add_menu_page('My page','My page','manage_options','my_page', $func );

Note you need PHP 5.3 to do that.