将动态值放在$ _POST中

I want to use a code like

foreach($_POST[cat_id] as $key=>$val){
                if($val){
                $arr[cat_id] = $val;
                $arr[porder] = $_POST['".$val."'];
                $arr[store_user_id] =$_SESSION[uid];        
                }
            }

but $_POST['".$val."'] will not cover any value but in my loop put the name dynamically can any one help me I want to show value of $_POST['".$val."'] which comes dynamically. I also use $_POST['<?=$val?>'] but it does not work.. please help...

Just use $_POST[$val] in place of $_POST['".$val."']

have you tried this way:

$arr[cat_id] = $_POST[$val] 

?