use Asad\OAuth2\Client\Provider\Zoho;

$provider = new Zoho([
    'clientId' => '{zoho-client-id}',
    'clientSecret' => '{zoho-client-secret}',
    'redirectUri' => 'http://localhost:8000/zoho/oauth2',
    'dc' => 'AU' //It will be optional if your ZOHO are in US location
]);

if (!isset($_GET['code'])) {
    // If we don't have an authorization code then get one
    $authUrl = $provider->getAuthorizationUrl([
        'scope' => [
            'ZohoCRM.modules.ALL', //Important: Define your data accessability scope here
            'ZohoCRM.settings.ALL',
        ],
        'access_type' => 'offline', //Important: If you want to generate the refresh token, set this value as offline
        'prompt' => 'consent'       //Important: Will not return a refresh token if this is not also set
    ]);

    $_SESSION['oauth2state'] = $provider->getState();
    header('Location: ' . $authUrl);
    exit;

    // Check given state against previously stored one to mitigate CSRF attack
} elseif (empty($_GET['state']) || ($_GET['state'] !== $_SESSION['oauth2state'])) {

    unset($_SESSION['oauth2state']);
    exit('Invalid state');
} else {

    // Try to get an access token (using the authorization code grant)
    try {
        $token = $provider->getAccessToken('authorization_code', [
            'code' => $_GET['code']
        ]);

        //$user = $provider->getResourceOwner($token);


        echo $access_token = $token->getToken();

        echo $refresh_token = $token->getRefreshToken(); //Save this refresh token to somewehre

        echo $token->getExpires();

    } catch (\Exception $e) {
        //handle you exception
    }
}

use Asad\OAuth2\Client\Provider\Zoho;
use League\OAuth2\Client\Grant\RefreshToken;

$provider = new Zoho([
    'clientId' => '{zoho-client-id}',
    'clientSecret' => '{zoho-client-secret}',
    'dc' => 'AU' //It will be optional if your ZOHO are in US location
]);

$refreshToken = 'FromYourStoredData';
$grant = new RefreshToken();
$token = $provider->getAccessToken($grant, ['refresh_token' => $refreshToken]);