Performs a true array intersection (array_uintersect will keep items in a1 even if they are not present in a2, a3, etc.)

array-intersect.php

$combined = array_filter($array1, function ($a) use ($array2) {
    $found = array_filter($array2, function ($b) use ($a) {
        return ((int) $a->ID) === ((int) $b->ID);
    });

    return !empty($found);
});