Integrating Recurly Subscription Billing with CakePHP is very simple.

Download Recurly PHP Client from the GitHub project site or download as a zip file.

Step 1:Unzip files to /app/Vendors folder

Step 2: On top of the controller, add import Vendor code. Example :

App::import('Vendor', 'Recurly',  array('file' => 'recurly-client'. DS . 'lib'.  DS  . 'recurly.php'));

Step 3: Get API Key and Private Key from Recurly site.

Step 4: Use code in any method will work

// Required for the API
Recurly_Client::$apiKey = 'Your api key';
// Optional for Recurly.js:
Recurly_js::$privateKey = 'your private key';
$account = new Recurly_Account();
$account->account_code = 'account_code';
$account->email = '';
$account->first_name = 'Verena';
$account->last_name = 'Example';

$account->billing_info = new Recurly_BillingInfo();
$account->billing_info->first_name = $account->first_name;
$account->billing_info->last_name = $account->last_name;
$account->billing_info->number = '4111-1111-1111-1111';
$account->billing_info->verification_value = '123';
$account->billing_info->month = 11;
$account->billing_info->year = 2015;
$account->billing_info->ip_address = $_SERVER['REMOTE_ADDR'];


for more details of Recurly PHP Client API functions visit this link PHP Client Library