Laravel 4.2
Mailchimp Library: https://github.com/hugofirth/laravel-mailchimp
I have already created a list and added two subscribers in Mailchimp GUI.
<?php
$list_id = '******';
$email_address = '[email protected]';
$subscriber = MailchimpWrapper::lists()->subscribe( 
                 $list_id, array('email'=>$email_address) 
              );    
return Response::json ( [ 
    'response'  => $subscriber
] );
?>
Response is true
{
  "response": {
    "email": "[email protected]",
    "euid": "d77e6cff13",
    "leid": "50083933"
  }
}
But when i check on mailchimp list, I see only 2 emails, the ones that I added via Mailchimp.
                        
I'm not super familiar with the laravel library, but typically this happens when you forget to set double-opt-in to false. [email protected] likely got sent a double opt-in confirmation message.