Attachment Handler Question

I have a question about the attachment handler. This question is in regards to getAttachmentConstraints(), and I was wondering if it is possible to implement a public function into the attachment handler class I have created. Any detailed explanation would be appreciated as this is my first addon in XenForo, and I'm a bit rusty on php. Below is an example of how I tried to implement it, and I'm just unsure how to go about getting this to work.

class GFLReleases_AttachmentHandler_Releases extends XenForo_AttachmentHandler_Abstract
    public function getAttachmentConstraints()
        $params = parent::getAttachmentConstraints();
        $options = XenForo_Application::get('options');
        $params['extensions'] = preg_split('/\s+/', trim($options->GFLReleases_screenshotExtensions));
        return $params;
This is not the complete file as I already have coded all the other necessary functions. What I am trying to do with is to only allow the uploading of images through the attachment system, but only for my addon and not the entire forum. So I only want to allow certain image types to be uploaded, and I am just having some issues with getting this to work. Now the preg_split is from the actual XenForo function in the Attachment Model. I am not sure if it's the correct way of doing it or if it can even be done, but wanted to ask. I have been programming visual basic for the past year and a half so I'm very rusty with php so I may have missed something.

Edit: After getting some rest I figured out the problem and was able to get it working.