Kit SDK PHP

The Kit PHP SDK provides convinient access to the Kit API from applications written in the PHP language.

It includes a pre-defined set of methods for interacting with the API.

Version Guidance

SDK Version	API Version	API Authentication	PHP Version
1.x	v3	API Key and Secret	7.4+
2.x	v4	OAuth	8.0+
2.2+	v4	API Key	8.0+

Refer to this guide for changes when upgrading to the v2 SDK.

Composer

You can install this PHP SDK via Composer. Run the following command:

composer require convertkit/convertkitapi

To use the PHP SDK, use Composer's autoload:

require_once 'vendor/autoload.php';

Dependencies

The PHP SDK require the following extensions in order to work properly:

• curl, although you can use your own non-cURL client if you prefer
• json
• mbstring (Multibyte String)

If you use Composer, these dependencies should be handled automatically.

Getting Started

2.x (v4 API, OAuth, PHP 8.0+)

First, register your OAuth application in the OAuth Applications section at https://app.kit.com/account_settings/advanced_settings.

Using the supplied Client ID and secret, redirect the user to Kit to grant your application access to their Kit account.

// Require the autoloader (if you're using a PHP framework, this may already be done for you).
require_once 'vendor/autoload.php';

// Initialize the API class.
$api = new \ConvertKit_API\ConvertKit_API(
    clientID: '<your_oauth_client_id>',
    clientSecret: '<your_oauth_client_secret>'
);

// Redirect to begin the OAuth process.
header('Location: '.$api->get_oauth_url('<your_redirect_uri>'));

Once the user grants your application access to their Kit account, they'll be redirected to your Redirect URI with an authorization code. For example:

your-redirect-uri?code=<auth_code>

At this point, your application needs to exchange the authorization code for an access token and refresh token.

$result = $api->get_access_token(
    authCode: '<auth_code>',
    redirectURI: '<your_redirect_uri>'
);

$result is an array comprising of:

• access_token: The access token, used to make authenticated requests to the API
• refresh_token: The refresh token, used to fetch a new access token once the current access token has expired
• created_at: When the access token was created
• expires_in: The number of seconds from created_at that the access token will expire

Once you have an access token, re-initialize the API class with it:

// Initialize the API class.
$api = new \ConvertKit_API\ConvertKit_API(
    clientID: '<your_oauth_client_id>',
    clientSecret: '<your_oauth_client_secret>',
    accessToken: '<your_access_token>'
);

To refresh an access token:

$result = $api->refresh_token(
    refreshToken: '<your_refresh_token>',
    redirectURI: '<your_redirect_uri>'
);

$result is an array comprising of:

• access_token: The access token, used to make authenticated requests to the API
• refresh_token: The refresh token, used to fetch a new access token once the current access token has expired
• created_at: When the access token was created
• expires_in: The number of seconds from created_at that the access token will expire

Once you have refreshed the access token i.e. obtained a new access token, re-initialize the API class with it:

// Initialize the API class.
$api = new \ConvertKit_API\ConvertKit_API(
    clientID: '<your_oauth_client_id>',
    clientSecret: '<your_oauth_client_secret>',
    accessToken: '<your_new_access_token>'
);

API requests may then be performed:

$result = $api->add_subscriber_to_form(12345, 'joe.bloggs@kit.com');

To determine whether a new entity / relationship was created, or an existing entity / relationship updated, inspect the HTTP code of the last request:

$result = $api->add_subscriber_to_form(12345, 'joe.bloggs@kit.com');
$code = $api->getResponseInterface()->getStatusCode(); // 200 OK if e.g. a subscriber already added to the specified form, 201 Created if the subscriber added to the specified form for the first time.

The PSR-7 response can be fetched and further inspected, if required - for example, to check if a header exists:

$result = $api->add_subscriber_to_form(12345, 'joe.bloggs@kit.com');
$api->getResponseInterface()->hasHeader('Content-Length'); // Check if the last API request included a `Content-Length` header

2.2+ (v4 API, API Key, PHP 8.0+)

Get your Kit API Key and API Secret here and set it somewhere in your application.

// Require the autoloader (if you're using a PHP framework, this may already be done for you).
require_once 'vendor/autoload.php';

// Initialize the API class.
$api = new \ConvertKit_API\ConvertKit_API(
    apiKey: '<your_v4_api_key>'
);

1.x (v3 API, API Key and Secret, PHP 7.4+)

Get your Kit API Key and API Secret here and set it somewhere in your application.

// Require the autoloader (if you're using a PHP framework, this may already be done for you).
require_once 'vendor/autoload.php';

// Initialize the API class.
$api = new \ConvertKit_API\ConvertKit_API('<your_public_api_key>', '<your_secret_api_key>');

Handling Errors

The Kit PHP SDK uses Guzzle for all HTTP API requests. Errors will be thrown as Guzzle's ClientException (for 4xx errors), or ServerException (for 5xx errors).

try {
    $forms = $api->add_subscriber_to_form('invalid-form-id');
} catch (GuzzleHttp\Exception\ClientException $e) {
    // Handle 4xx client errors.
    die($e->getMessage());
} catch (GuzzleHttp\Exception\ServerException $e) {
    // Handle 5xx server errors.
    die($e->getMessage());
}

For a more detailed error message, it's possible to fetch the API's response when a ClientException is thrown:

// Errors will be thrown as Guzzle's ClientException or ServerException.
try {
    $forms = $api->form_subscribe('invalid-form-id');
} catch (GuzzleHttp\Exception\ClientException $e) {
    // Handle 4xx client errors.
    // For ClientException, it's possible to inspect the API's JSON response
    // to output an error or handle it accordingly.
    $error = json_decode($e->getResponse()->getBody()->getContents());
    die($error->message); // e.g. "Entity not found".
} catch (GuzzleHttp\Exception\ServerException $e) {
    // Handle 5xx server errors.
    die($e->getMessage());
}

Documentation

See the PHP SDK docs

Contributing

See our contributor guide for setting up your development environment, testing and submitting a PR.

For Kit, refer to the deployment guide on how to publish a new release.