// Generate an authorization URL for the Authorization Code flow
$client->oauth()->getAuthorizationUrl(
    string $clientId,
    string $redirectUri,
    string $scope,
    string $state,
    string $codeChallenge,
    string $codeChallengeMethod = 'S256'
): string
// Exchange an authorization code for tokens
$client->oauth()->exchangeCode(
    string $clientId,
    string $clientSecret,
    string $code,
    string $redirectUri,
    string $codeVerifier
): array
// Refresh an access token using a refresh token
$client->oauth()->refreshToken(
    string $clientId,
    string $clientSecret,
    string $refreshToken
): array
// Obtain an access token using Client Credentials grant
$client->oauth()->clientCredentials(
    string $clientId,
    string $clientSecret,
    string $scope = ''
): array
// Revoke an access or refresh token
$client->oauth()->revokeToken(
    string $clientId,
    string $clientSecret,
    string $token
): array

// Step 1: Generate PKCE values
$codeVerifier  = bin2hex(random_bytes(32));
$codeChallenge = rtrim(strtr(base64_encode(hash('sha256', $codeVerifier, true)), '+/', '-_'), '=');
// Step 2: Redirect user to authorization URL
$authUrl = $client->oauth()->getAuthorizationUrl(
    clientId:            'my-client-id',
    redirectUri:         'https://myapp.com/oauth/callback',
    scope:               'licenses:read customers:read',
    state:               bin2hex(random_bytes(16)),
    codeChallenge:       $codeChallenge,
    codeChallengeMethod: 'S256'
);
header('Location: ' . $authUrl);
// Step 3: After redirect, exchange the code
$tokens = $client->oauth()->exchangeCode(
    clientId:     'my-client-id',
    clientSecret: 'my-client-secret',
    code:         $_GET['code'],
    redirectUri:  'https://myapp.com/oauth/callback',
    codeVerifier: $codeVerifier
);
$accessToken  = $tokens['access_token'];
$refreshToken = $tokens['refresh_token'];

$tokens = $client->oauth()->clientCredentials(
    clientId:     'my-client-id',
    clientSecret: 'my-client-secret',
    scope:        'licenses:read products:read'
);
$accessToken = $tokens['access_token'];