Callbacks

Callbacks

Callbacks (within the context of this library) are functions to be executed upon the completion of a request. There are two kinds of callbacks that can be set, Success Callbacks and Failure Callbacks. In both cases when setting a callback they must fulfill the PHP definition of a callable. In the case of a SuccessResponse or a FailureResponse, the first and only argument given to your callback will be an instance of the response object itself as shown in the below examples. It is also important to note that callbacks do persist from request to request and will need to be reset manually.

The PHP definition of a callable can be found in this documentation: http://php.net/manual/en/language.types.callable.php

Success Callbacks

A success callback is a function that will be executed once a response from MailChimp has been evaluated as being a "successful" response. In this context, that means that the response contained an HTTP code within the 200 range. When this library receives a response from the MailChimp API it decides whether its a success response or a failure response and returns either a SuccessResponse or FailureResponse object. Both of which are instances of a MailchimpResponse. The callbacks for each are executed in their respective class constructors. Assuming we have a valid instance of the Mailchimp class we can set a success callback like this:

$func = function (MailchimpResponse $response) {
    print $response->getHttpCode();
};

$mailchimp->request->setSuccessCallback($func);

Now when we make a request and the response indicates it was successful the anonymous function $func will be executed.

$mailchimp
    ->account
    ->get();

//Outputs: 200

Failure Callbacks

A failure callback is executed when a response is interpreted as a failure response. This means that the HTTP code for this response was outside of the 200 range. An example of this might be attempting to retrieve a resource that does not exist (which would typically return a 404). We can set a failure callback like this:

$func = function (MailchimpResponse $response) {
    print $response->getHttpCode();
};

$mailchimp->request->setFailureCallback($func);

Now lets make a request against a resource that does not exist:

$mailchimp
    ->lists("not list id")
    ->get();

//Outputs: 404