Fluent Conditional Validation for PHP

FEREGOTTO Romain — Thu, 22 Jan 2026 12:22:06 +0000

PHP Conditional Validation Without the Mess

Every PHP developer has written this at some point:

if ($data['account_type'] === 'business') {
    if (empty($data['company_name'])) {
        $errors[] = 'Company name is required';
    }
    if (empty($data['vat_number'])) {
        $errors[] = 'VAT number is required';
    }
    // ... and more
}

It works. It's also a maintenance nightmare.

The Problem

Conditional validation — where field A is required only when field B has a specific value — is everywhere:

Registration: VAT number required only for business accounts
E-commerce: shipping address required only for physical delivery
Multi-step forms: fields depend on previous selections

Most PHP validation libraries handle simple cases well. But conditional logic? You end up with callbacks, closures, or falling back to manual if/else blocks.

Here's Valitron:

$v->rule('required', 'vat_number')->when(function($data) {
    return $data['account_type'] === 'business';
});

Here's Respect Validation:

v::key('account_type', v::equals('business'))
    ->key('vat_number', v::notEmpty());
// Wait, that's not even conditional...

The syntax gets verbose fast, especially with nested conditions.

A Different Approach

I wanted something that reads like the requirement:

"When account_type equals business, then vat_number is required"

So I built it:

$dv = new DataVerify($registrationData);

$dv
    ->field('email')->required->email
    ->field('account_type')->required->in(['personal', 'business'])
    ->field('country')->required->in(['FR', 'DE', 'ES'])

    ->field('vat_number')
        ->when('account_type', '=', 'business')
        ->and('country', '=', 'FR')
        ->then->required->regex('/^FR\d{11}$/')

    ->field('vat_number')
        ->when('account_type', '=', 'business')
        ->and('country', '=', 'DE')
        ->then->required->regex('/^DE\d{9}$/')

    ->field('vat_number')
        ->when('account_type', '=', 'business')
        ->and('country', '=', 'ES')
        ->then->required->regex('/^ES[A-Z0-9]\d{7}[A-Z0-9]$/');

if (!$dv->verify()) {
    $errors = $dv->getErrors();
}

The when/and/then syntax maps directly to business rules. No callbacks, no closures, no mental gymnastics.

Nested Objects

Real-world data is rarely flat. API payloads have nested structures:

$data = [
    'user' => [
        'email' => 'john@example.com',
        'profile' => [
            'name' => 'John',
            'age' => 25
        ]
    ],
    'order' => [
        'items' => [...]
    ]
];

Validation handles it naturally:

$dv->field('user')->required->object
    ->subfield('email')->required->email
    ->subfield('profile')->required->object
        ->subfield('name')->required->string
        ->subfield('age')->int->between(18, 120);

Conditions can reference nested paths too:

$dv->field('billing_address')
    ->when('user.type', '=', 'business')
    ->then->required;

Reusable Rules & Schemas

Define validation patterns once, reuse everywhere:

// Rules: reusable validation chains (field-agnostic)
DataVerify::registerRules('password_rules')
    ->minLength(12)->containsUpper->containsLower->containsNumber;

$dv->field('password')->required->rule('password_rules');
$dv->field('password_confirm')->required->rule('password_rules');

For complete validation structures, use schemas:

// Schemas: full validation blueprints with fields + conditions
DataVerify::registerSchema('checkout')
    ->field('email')->required->email
    ->field('delivery_type')->required->in(['shipping', 'pickup'])
    ->field('shipping_address')
        ->when('delivery_type', '=', 'shipping')
        ->then->required->string;

// Apply in one line
$dv = new DataVerify($data);
$dv->schema('checkout');

What It's Not

This isn't a Laravel replacement. If you're in a framework with built-in validation, use that.

This is for:

Legacy codebases without a framework
Microservices and APIs with custom validation needs
Projects where minimizing transitive dependencies matters (easier auditing, reduced supply chain risk)
Anyone tired of callback-based conditional validation

The Code

It's MIT licensed, zero dependencies, PHP 8.1+:

GitHub: github.com/gravity-zero/dataVerify

Install: composer require gravity/dataverify

Feedback welcome — I'm actively maintaining it and open to suggestions/contributers.

What's your current approach to conditional validation in PHP? Curious to hear how others handle this.

Forem: FEREGOTTO Romain