$all_display = array();
$ad_all->each(function($ad){
$all_display[] =array('num'=>$ad->num);
});
print_r($all_display);
alternative
$all_display = array();
$ad_all->each(function($ad) use ($all_display){
$all_display[] =array('num'=>$ad->num);
});
print_r($all_display);
$ad_all has four rows, but when I print $all_display, it doesn't display anything.