Our Customer Support staff that handle phone support are skilled for helping customers use our User Interface/website (the UI), but support of the Application Programming Interface (API) that applications use to access account functions is a far more technical topic, so your request has been moved to our Developer Support Forum.
Our API allows access to contact and list management functions, and campaign creation and scheduling (with permission) functions though HTTP Requests to our API servers, and these can be done through a PHP application.
The short answer to your question is "yes," but with the caveat that the programming to control frequency of emails, and any list/contact management actions requires to vary frequencies of individual or groups of contacts, from your Constant Contact musts all be accomplished through your app/integration's programming.
Links to a variety of code samples, including a PHP Wrapper Library, which handles the most difficult parts of programming HTTP requests to our API, making it easier for developers to integrate, can be found on http://developer.constantcontact.com, along with our API Documentation, which provides technical requirements for requests to our API.
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