致命错误：第12行的C：\ xampp \ htdocs \ cart \ app \ Validation \ Forms \ OrderForm.php中找不到类'Respect \ Validation \ Validator'

I installed respect/validation with composer but when using it with my work I get this error when loading the page.

"Fatal error: Class 'Respect\Validation\Validator' not found in C:\xampp\htdocs\cart\app\Validation\Forms\OrderForm.php on line 12"

This is the code of the page it is on:

<?php

namespace Cart\Validation\Forms;

use Respect\Validation\Validator as v;

class OrderForm
{
    public static function rules()
    {
        return[
            'email' => v::email(),
            'name' => v::alpha(' '),
            'address1' => v::alnum(' -'),
            'address2' => v::optional(v::alnum(' -')),
            'city' => v::alnum(' '),
            'postal_code' => v::alnum(' '),
        ]; 
    }
}