Validation

Marko’s validation system provides clear, composable rules for validating input data. Inject ValidatorInterface and define rules as simple arrays --- validate() returns a ValidationErrors object you can inspect, or use validateOrFail() to throw on failure.

Setup

composer require marko/validation

Basic Validation

<?php

declare(strict_types=1);

use Marko\Validation\Contracts\ValidatorInterface;
use Marko\Validation\Validation\ValidationErrors;

class PostController
{
    public function __construct(
        private readonly ValidatorInterface $validator,
    ) {}

    public function store(array $data): void
    {
        $errors = $this->validator->validate($data, [
            'title' => ['required', 'string', 'min:3', 'max:200'],
            'body' => ['required', 'string'],
            'email' => ['required', 'email'],
            'status' => ['in:draft,published'],
        ]);

        if ($errors->isNotEmpty()) {
            // Handle validation errors
            // $errors->all() returns ['field' => ['message', ...]]
        }
    }
}

Handling Validation Errors

The validate() method returns a ValidationErrors object:

use Marko\Validation\Contracts\ValidatorInterface;
use Marko\Validation\Validation\ValidationErrors;

$errors = $this->validator->validate($data, $rules);

if ($errors->isNotEmpty()) {
    $errors->all();           // ['title' => ['The title field is required.']]
    $errors->has('title');    // true
    $errors->get('title');    // ['The title field is required.']
    $errors->first('title');  // 'The title field is required.'
}

To throw an exception on validation failure, use validateOrFail():

use Marko\Validation\Contracts\ValidatorInterface;
use Marko\Validation\Exceptions\ValidationException;

try {
    $this->validator->validateOrFail($data, $rules);
} catch (ValidationException $e) {
    $errors = $e->errors(); // ValidationErrors instance
}

Available Rules

Rule	Description
required	Field must be present and not empty
string	Must be a string
int	Must be an integer
email	Must be a valid email address
min:n	Minimum length (string) or value (number)
max:n	Maximum length (string) or value (number)
in:a,b,c	Must be one of the listed values
url	Must be a valid URL
confirmed	Must have a matching _confirmation field

Next Steps

• Routing — validate request input in controllers
• Error Handling — customize error responses
• Validation package reference — full API details