<?php
include 'vendor/autoload.php';
if(isset($_REQUEST['code']))
{
    die('<pre>'.print_r(array_keys($_REQUEST), true));
}
$clientId ='6b14062f3c4';
$clientSecret= 'q50Hqip2VlCGUdUGMDBqkw';
$redirectUri = 'gkvector.loc/demo';
$state = 'gkvector.loc';
$apiClient = new \AmoCRM\Client\AmoCRMApiClient($clientId, $clientSecret, $redirectUri);

echo $apiClient->getOAuthClient()->getOAuthButton(
    [
        'title' => 'Установить интеграцию',
        'compact' => true,
        'class_name' => 'className',
        'color' => 'default',
        'error_callback' => 'handleOauthError',
        'state' => $state,
    ]
);