Array
(
    [1880] => Array
        (
            [parent_category_id] => 1880
            [parent_category] => Array
                (
                    [id] => 1880
                    [slug] => engineering
                    [name] => Engineering
                )

            [subcategories] => Array
                (
                    [0] => Array
                        (
                            [name] => Electrical Engineering
                            [slug] => electrical-engineering
                            [id] => 1882
                        )

                )

        )

    [1723] => Array
        (
            [parent_category_id] => 1723
            [parent_category] => Array
                (
                    [id] => 1723
                    [slug] => math
                    [name] => Math
                )

            [subcategories] => Array
                (
                    [0] => Array
                        (
                            [name] => Algebra 1
                            [slug] => algebra-1
                            [id] => 1725
                        )

                    [1] => Array
                        (
                            [name] => Calculus
                            [slug] => calculus
                            [id] => 1730
                        )

                    [2] => Array
                        (
                            [name] => Linear Algebra
                            [slug] => linear-algebra
                            [id] => 1733
                        )

                    [3] => Array
                        (
                            [name] => Probability
                            [slug] => probability
                            [id] => 1735
                        )

                )

        )

)