php post遍历问题

print_r($_REQUEST);

取到的值是

Array
(
    [c] => pay2
    [cart] => 1
    [itemid] => Array
        (
            [0] => 103
            [1] => 104
            [2] => 105
            [3] => 106
        )

    [PHPSESSID] => rdkrfasknosmg58o1r1d9i6pf5
)

foreach ($_REQUEST as $key => $value) 
{
    echo "Key: $key; Value: $value<br />\n";
}

遍历不能遍历出itemid ，如何才能遍历成1,2,3这样
[解决办法]
foreach ($_REQUEST as $key => $value)
{
if(is_array($value)) $value = join(',', $value);
echo "Key: $key; Value: $value<br />\n";
}