The following does the job:
add_action( 'admin_init','wpse_60168_custom_menu_class' );
function wpse_60168_custom_menu_class()
{
global $menu;
foreach( $menu as $key => $value )
{
if( 'Posts' == $value[0] )
$menu[$key][4] .= " custom-class-1";
if( 'Pages' == $value[0] )
$menu[$key][4] .= " custom-class-2";
}
}
And if you want to inspect what the $menu
contains, use this:
add_action( 'admin_init','wpse_60168_var_dump_and_die' );
function wpse_60168_var_dump_and_die()
{
global $menu;
echo '<pre>' . print_r( $menu, true ) . '</pre>';
wp_die();
}