AdWordsSession $session,
$session = (new AdWordsSessionBuilder())->fromFile()->withOAuth2Credential($oAuth2Credential)->build();
You could refer to CreateAccount.php sample code
here. In this example you could remove the code from line number 49 to 73 and add the code snippet shared previously to send the invitation. To authenticate your MCC account, you need to create OAuth credentials for the login email id of your MCC account. Please refer this
guide to create OAuth credentials. Let me know if you are facing an issue.