Dynamic Form Validation in Laravel with prohibited_if

Laravel's prohibited_if validation rule simplifies handling interdependent form fields. This rule elegantly restricts field inputs based on the values of other fields, enhancing dynamic form validation.

Understanding prohibited_if

The prohibited_if rule ensures specific fields remain empty if a condition is met. This is particularly useful for dynamic forms with interconnected fields.

Example:

use Illuminate\Support\Facades\Validator;

$validator = Validator::make($request->all(), [
    'freelance_company' => 'prohibited_if:type,individual',
    'type' => 'required|in:individual,business'
]);

Real-World Application: Membership Registration

Consider a professional membership registration system:

<?php namespace App\Http\Controllers;

use App\Models\Membership;
use Illuminate\Http\Request;
use Illuminate\Validation\Rule;

class MembershipController extends Controller
{
    public function store(Request $request)
    {
        $request->validate([
            'membership_type' => 'required|in:personal,corporate',
            'full_name' => 'required|string|max:255',
            'organization_name' => [
                'prohibited_if:membership_type,personal',
                'required_if:membership_type,corporate',
                'string',
                'max:255',
            ],
            'organization_size' => [
                'prohibited_if:membership_type,personal',
                'required_if:membership_type,corporate',
                'integer',
                'min:1',
            ],
            'tax_id' => [
                Rule::prohibitedIf(fn() =>
                    $request->membership_type === 'personal' ||
                    $request->country !== 'US'
                ),
                'string',
                'size:9',
            ],
        ], [
            'organization_name.prohibited_if' => 'Organization details are unnecessary for personal memberships.',
            'tax_id.prohibited_if' => 'Tax ID is only needed for US-based corporate memberships.',
        ]);
        Membership::create($request->validated());
        return response()->json([
            'message' => 'Membership created successfully'
        ]);
    }
}

This example showcases:

• Conditional field requirements based on membership_type.
• Tax ID validation for US corporate members only.
• Clear custom error messages.
• Integration with other validation rules.

Extending with Multiple Conditions:

You can add multiple conditions:

'business_license' => [
    Rule::prohibitedIf(fn() =>
        $request->membership_type === 'personal' ||
        !in_array($request->business_type, ['retail', 'franchise'])
    ),
    'required_if:business_type,retail,franchise',
    'string',
]

prohibited_if allows for complex validation logic while maintaining code readability. This ensures your forms adapt to user input context effectively.

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