Laravel Validation - How can I make Rule::in() allow missing/null values?

Question

I use the Laravel validator to dynamically validate a field like so:

use Illuminate\Support\Facades\Validator;
use Illuminate\Validation\Rule;


                $validator = Validator::make(
                    data: (array)$parent,
                    rules: [
                        'code' => [Rule::in($allowedCodes)],
                    ]
                );

                if ($validator->fails()) { ... }

However, I want to be able to also allow missing/null values.

How can I do this? Adding null in the list of $allowedCodes does not seem to work.

Also, I try to avoid using the string representation of the in rule (that requires concatenating all allowed codes into a string.

Answer 1

To allow for both valid codes and null values in Laravel's Validator, you can modify your rule slightly. Instead of directly adding null to the $allowedCodes array (which doesn't work with Rule::in), you should ensure that null is treated as a valid value by using a conditional rule in your validation.

According to the example in the documentation (https://laravel.com/docs/11.x/validation#rule-in):

use Illuminate\Support\Facades\Validator;
use Illuminate\Validation\Rule;

$validator = Validator::make(
    data: (array)$parent,
    rules: [
        'code' => ['nullable', Rule::in($allowedCodes)],
    ]
);

if ($validator->fails()) {
    // Handle validation failure
}

Alternative (using custom validation): If for some reason you need a more custom approach (such as adding more complex validation for null), you can use a custom validation rule (example in the documentation https://laravel.com/docs/11.x/validation#using-closures ):

$validator = Validator::make(
    data: (array)$parent,
    rules: [
        'code' => [
            'nullable',
            function ($attribute, $value, $fail) use ($allowedCodes) {
                if (!is_null($value) && !in_array($value, $allowedCodes)) {
                    $fail($attribute.' is invalid.');
                }
            },
        ],
    ]
);