<?phpnamespace DevCoder\Validator;use DevCoder\Validator\Assert\ValidatorInterface;use InvalidArgumentException;use Psr\Http\Message\ServerRequestInterface;use function array_map;use function array_merge;use function get_class;use function gettype;use function is_array;use function is_object;use function is_string;use function sprintf;use function trim;class Validation{    /**     * @var array<string,array>     */    private $validators;    /**     * @var array<string,string>     */    private $errors = [];    /**     * @var array     */    private $data = [];    public function __construct(array $fieldValidators)    {        foreach ($fieldValidators as $field => $validators) {            if (!is_array($validators)) {                $validators = [$validators];            }            $this->addValidator($field, $validators);        }    }    public function validate(array $data): bool    {        $this->data = $data;        /**         * @var $validators array<ValidatorInterface>         */        foreach ($this->validators as $field => $validators) {            if (!isset($this->data[$field])) {                $this->data[$field] = null;            }            foreach ($validators as $validator) {                if ($validator->validate($this->data[$field]) === false) {                    $this->addError($field, (string)$validator->getError());                }            }        }        return $this->getErrors() === [];    }    /**     * @return array<string,string>     */    public function getErrors(): array    {        return $this->errors;    }    /**     * @return array     */    public function getData(): array    {        return $this->data;    }    private function addError(string $field, string $message): void    {        $this->errors[$field][] = $message;    }    /**     * @param string $field     * @param array<ValidatorInterface> $validators     * @return void     */    private function addValidator(string $field, array $validators): void    {        foreach ($validators as $validator) {            if (!$validator instanceof ValidatorInterface) {                throw new InvalidArgumentException(sprintf(                    $field . ' validator must be an instance of ValidatorInterface, "%s" given.',                    is_object($validator) ? get_class($validator) : gettype($validator)                ));            }            $this->validators[$field][] = $validator;        }    }}

<?phpnamespace DevCoder\Validator\Assert;interface ValidatorInterface{    public function validate($value): bool;    public function getError(): ?string;}

<?phpnamespace DevCoder\Validator\Assert;abstract class AbstractValidator implements ValidatorInterface{    /**     * @var string|null     */    protected $error;    public function getError(): ?string    {        return $this->error;    }    protected function error(string $message, array $context): void    {        $replace = [];        foreach ($context as $key => $value) {            if (is_object($value)) {                $value = method_exists($value, '__toString') ? (string)$value : get_class($value);            } elseif (is_array($value)) {                $value = json_encode($value);            } else {                $value = (string)$value;            }            $replace['{{ ' . $key . ' }}'] = $value;        }        $this->error = strtr($message, $replace);    }}

<?phpdeclare(strict_types=1);namespace DevCoder\Validator\Assert;use function ctype_digit;use function is_int;use function strval;class Integer extends AbstractValidator{    /**     * @var string     */    private $invalidMessage = 'This value should be of type {{ type }}.';    private $minMessage = '{{ value }} should be {{ limit }} or more.';    private $maxMessage = '{{ value }} should be {{ limit }} or less.';    /**     * @var int|null     */    private $min;    /**     * @var int|null     */    private $max;    public function validate($value): bool    {        if ($value === null) {            return true;        }        if (ctype_digit(strval($value)) === false) {            $this->error($this->invalidMessage, ['value' => $value, 'type' => 'integer']);            return false;        }        if (is_int($this->min) && $value < $this->min) {            $this->error($this->minMessage, ['value' => $value, 'limit' => $this->min]);            return false;        }        if (is_int($this->max) && $value > $this->max) {            $this->error($this->maxMessage, ['value' => $value, 'limit' => $this->max]);            return false;        }        return true;    }    public function invalidMessage(string $invalidMessage): self    {        $this->invalidMessage = $invalidMessage;        return $this;    }    public function minMessage(string $minMessage): self    {        $this->minMessage = $minMessage;        return $this;    }    public function maxMessage(string $maxMessage): self    {        $this->maxMessage = $maxMessage;        return $this;    }    public function min(int $min): self    {        $this->min = $min;        return $this;    }    public function max(int $max): self    {        $this->max = $max;        return $this;    }}

<?phpdeclare(strict_types=1);namespace DevCoder\Validator\Assert;class NotNull extends AbstractValidator{    private $message = 'This value should not be null.';    public function validate($value): bool    {        if ($value === null) {            $this->error($this->message, ['value' => $value]);            return false;        }        return true;    }    public function message(string $message): self    {        $this->message = $message;        return $this;    }}

<?php$validation = new Validator([    'age' => [(new Integer())->min(18)->max(99), new NotNull()],    'number_of_children' => [new NotNull(), new Integer()],    'salary' => [new NotNull(), new Integer()],]);

<?phpif ($validation->validate($_POST) === true) {    $data = $validation->getData();    // save in database    // redirect in another page}return render('template.html.php', [    'errors' => $validation->getErrors()]);

$validation = new Validation([    'email' => [new NotNull(), new Email()],    'password' => new NotNull(),    'firstname' => [new NotNull(), (new StringLength())->min(3), new Alphabetic()],    'lastname' => [(new StringLength())->min(3)],    'gender' => new Choice(['Mme', 'Mr', null]),    'website' => [new NotNull(), new Url()],    'age' => [new NotNull(), (new Integer())->min(18)],    'invoice_total' => [new NotNull(), new Numeric()],    'active' => [new NotNull(), new Custom(function ($value) {        return is_bool($value);    })]]);