How to validate both the key and value of a request array

I think you can do something like this

$rules = [
    'sell.*' => 'required|sell|exists:stock,id',
    'sell.*.*' => 'required|sell|exists:exchange,id',
]);

Note: I didn't tested this at all!

Another solution would be structuring the data a bit differently.

{
    "sell": {
        "111":[
            {"id": 1},
            {"id": 2},
            {"id": 3}
        ]
    }
 }

I believe you can then do this in your validation

$rules = [
    'sell.*' => 'required|sell|exists:stock,id',
    'sell.*.id' => 'required|sell|exists:exchange,id',
]);

Documentation: https://laravel.com/docs/5.8/validation#validating-arrays

If this isn't working I would probably make my own custom validation rule to validate this really specific case!

thank you @bobbybouwmann

I am trying first method for just the first key validation and getting validator error: BadMethodCallException: Method [validateSell] does not exist... Validator.php

I'm using it in Rules class

$rules = [ 'sell.*' => 'required|sell|exists:stock,id' ]

and in controller calling it

$this->validate($request, $this->tradeRules->getRules($request));

Any thoughts - there is no validateSell method I have to explicitly create ?

I'm assuming the validation string required|<request element>|exists: <table>, <field> ?

in laravel 8.82.0 and above you have a new rule called "required_array_keys" https://laravel.com/docs/9.x/validation#rule-required-array-keys it validates that your key must be included in the values you set with the validation rule.