PHP / MongoDB - 从多个文档中提取记录，光标在第一个记录上执行后死亡

I wrote a script to find all records in a collection, and tell me if the user needs to be emailed, does not need to be emailed, or has unsubscribed from email.

I can get it to tell me this information, however when adding an action as simple as echoing a test email template ($m), the scripts dies after passing over one record, resulting in error:

"Error connecting to MongoDB server the connection has been terminated, and this cursor is dead"

Code:

$date = date('Y-m-d');
$pastdate = date('Y-m-d', strtotime('-1 week'));
                try {
                    $conn = new Mongo('localhost');
                    $db = $conn->remo;
                    $c = $db->data;
                    $cursor = $c->find( array('last_email'=>array('$nin' => array())));
                    foreach($cursor as $obj) { 
                        if (($obj['last_email'] == null) || ($obj['last_email'] <= $pastdate)) {
                            if($obj['weeklyemail'] === '1') {
                                //Debugging
                                echo 'email'.$obj['email'];
                                //Message to send
                                $m = "Hello ".$obj['first_name'].", this is a test.";
                                echo $m;
                                //Do the mail

                               //Update the date for last_email for user
                                    $newdate = array('$set' => array('last_email' => $date));
                                    $cursor->update(array('email' => ''.$obj['email'].''), $newdate);

                            } else {
                                echo 'unsubscribed'.$obj['email'];
                            }
                        } else {
                            echo 'noemail'.$obj['email'];
                        }
                    }

                // disconnect from server
                $conn->close();
                }  catch (MongoConnectionException $e) {
                    die('Error connecting to MongoDB server' . $e->getMessage());
                } catch (MongoException $e) {
                    die('Error: ' . $e->getMessage());
                }

I am confused why the script works, until I simply add an echo. I am expecting the message ($m) to be echoed for each user that needs the email. Once I can get a simple echo to work, I plan on adding the script for the actual mailer part.