You have to be a bit more specific about what you want to do with an MCC account. The most common use case is to fetch all accounts in the MCC, allow user to pick an AdWords account, and then perform campaign management operations on it. You can find relevant code examples in
https://github.com/googleads/googleads-php-lib/tree/master/examples/AdWords/v201409/AccountManagement. The way you make API calls are similar - you use an OAuth2 access token for your MCC account instead of AdWords account, and set clientCustomerId SOAP header to the relevant AdWords account when making the call.