Write to array in array

I need to write an array to an array. Is this possible even possible? Like e.g.

`rules.php`
```php
return [
'rules' => [
       [
            'name' => 'Test rule',
            'value' => 'value1'
        ],
        [
            'name' => 'Test rule 2',
            'value' => 'value 2'
        ]
    ]
]
```