Use Rule::prohibitedIf() and Rule::prohibited() to ensure specific fields cannot be submitted based on other form selections.
When building forms with mutually exclusive options (such as submitting a company tax ID when account type is 'individual', or submitting credit card details when payment method is 'paypal'), accepting invalid fields can cause billing bugs.
Laravel provides the prohibited and prohibited_if validation rules.
Using Rule::prohibitedIf() in Form Requests
use Illuminate\Validation\Rule;
public function rules(): array
{
return [
'account_type' => ['required', 'in:individual,business'],
// Tax ID is strictly prohibited if account type is 'individual'
'tax_id' => [
Rule::prohibitedIf($this->account_type === 'individual'),
'string',
'max:20',
],
'payment_method' => ['required', 'in:card,paypal'],
// Card number cannot be submitted if payment method is 'paypal'
'card_number' => [
Rule::prohibitedIf($this->payment_method === 'paypal'),
'nullable',
'numeric',
],
];
}Summary
- Fails validation if prohibited fields are present in the request payload.
- Accepts boolean conditions or closure evaluations.
- Guarantees strict mutually exclusive input validation.
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