wordpress - add_menu_page not working with in-class function -

i'am trying use add_menu_page create custom "custom_post" page. (is mistake or not ? :-/)

here's code won't work :

add_menu_page( 'projets' , 'projets' , 'edit_posts', 'ajouter_projet' , array( $this, 'afficher_admin_page' ) , $img_url, 5);

but when use

add_menu_page( 'projets' , 'projets' , 'edit_posts', 'ajouter_projet' , afficher_admin_page' , $img_url, 5);

with function afficher_admin_page out of class, works.

what doing wrong ?

thank you

please use link

http://codex.wordpress.org/function_reference/add_menu_page

this helps you.

Back