Using $this when not in object context - Laravel 4 - php

Question

I have these two methods in my Contact.php model:
public function getSubscribers($listId)
{
return $this->withTrashed()
->where(DB::raw("concat('',email * 1)"), '!=', DB::raw('email'))
->where('opt_out', '0')
->select('email')
->chunk(1000, function($results) use ($listId) { $this->subscribeEmails($listId, $results); });
}
public function subscribeEmails($listId, $subscribers)
{
$emails = array();
foreach ($subscribers as $key => $subscriber)
{
$memberActivity = $subscriber->memberActivity($listId);
if ( ! $memberActivity['data'])
{
$emails[] = array('email' => $subscriber->email);
}
else
{
foreach ($memberActivity['data'] as $data)
{
foreach ($data['activity'] as $activity)
{
if ($activity['action'] !== 'unsub')
{
$emails[] = array('email' => $subscriber->email);
}
}
}
}
}
MailchimpWrapper::lists()->batchSubscribe($listId, $emails, false, true);
}
And the getSubscribers() method is called in my AdminContactsController.php controller via a method called updateMailchimp():
public function updateMailchimp()
{
$this->contact->getSubscribers($this->listId);
$message = (object) array(
'title' => 'Excellent!',
'content' => 'The Mailchimp newsletter list has been updated with the latest contacts from within the system.',
'alert_type' => 'success'
);
return Redirect::back()->with('message', $message);
}
Locally, this works great, no problems at all but on the staging server, I get the following error referencing the line cotaining ->chunk(1000, function($results) use ($listId) { $this->subscribeEmails($listId, $results); });:
Using $this when not in object context
Is this a PHP version issue or am I missing something here?

Answer 1

The reason why your code works on localhost but not on the remote server is probably the difference in PHP versions. Before PHP 5.4.0 it is not possible to use $this from anonymous function. You must pass the reference to $this within the use keyword:
public function getSubscribers($listId)
{
$that = $this; // <---- create reference to $this
return $this->withTrashed()
->where(DB::raw("concat('',email * 1)"), '!=', DB::raw('email'))
->where('opt_out', '0')
->select('email')
->chunk(1000, function($results) use (&$that, $listId) { $this->subscribeEmails($listId, $results); });
}