Your PHP Code Snippet

                    
<?php
declare(strict_types=1);

class Avatar
{
    public function __construct(
        private $data,
    ){}

    public function getAvatar(): string
    {
        $val = $this->data['avatar'];

        if(empty($val))
        {
            throw new ValidationException("Choose picture");
        }
        else if(!in_array($this->getExtension(), ['jpg', 'png', 'jpeg']))
        {
            throw new ValidationException("Incorrect extension");
        }
        return $val;

    }

    private function getExtension(): string
    {
        $val = $this->data['avatar'];

        return pathinfo($val, PATHINFO_EXTENSION);
    }
}

class ValidationException extends Exception {}