How can I assign to a var the current value of a form component for dependent forms?

[jechaviz]

Let's say I have a select input with value "My Selection", then I want to assign this value to $mySelectionValue,
And also I have a text input with value "My input", then I want to assign this also to a $myInputValue,
How can I achieve this?
Components\BelongsToSelect::make('category_id')
->relationship('category', 'name', function ($query) {
return $query->where($mySelectionValue, $myInputValue);
});

So I can create another dependent select and its query based on values from other form components values.