$array_8
$array_9

Array
(
    [0] => 8
    [1] => 9
)

<?php foreach ($arr_id as $id) { ?>
<?php foreach ($array_"тут номер $id" as $value) { ?>

Array
(
    [8] => [/* массив $array_8 */],
    [9] => [/* массив $array_9 */],
)

foreach ($arr_id as $id) {
    foreach (${'array_' . $id} as $value) {

foreach ($arr_id as $id) {
    $arr_name = 'array_' . $id;
    foreach (${$arr_name} as $value) {