marshal.php

<?php

function marshal(array $rows) {
    foreach ($rows as $row) {
        assert(is_object($row));
        assert(property_exists($row, "id"));
        assert(property_exists($row, "type"));

        $row->relatives = array_filter($rows, function ($next) use ($row) {
            $key = "{$row->type}_id";

            if (property_exists($next, $key)) {
                return $next->$key === $row->id;
            }
        });

        yield $row;
    }
}

$rows = json_decode(json_encode([
    ["type" => "blog", "id" => 1, "taxonomy_id" => 1],
    ["type" => "blog", "id" => 2, "taxonomy_id" => 2],
    ["type" => "post", "id" => 1, "blog_id" => 1, "taxonomy_id" => 1],
    ["type" => "post", "id" => 2, "blog_id" => 1, "taxonomy_id" => 2],
    ["type" => "post", "id" => 3, "blog_id" => 2, "taxonomy_id" => 1],
    ["type" => "post", "id" => 4, "blog_id" => 2, "taxonomy_id" => 2],
    ["type" => "taxonomy", "id" => 1],
    ["type" => "taxonomy", "id" => 2],
]));

print_r(
    iterator_to_array(
        marshal($rows)
    )
);