encoding.php
public function attach($key, $content, $filename)
    {
        $this->request[] = new SimpleAttachment($key, $content, $filename);
    }
public function attach($key, $content, $filename)
    {
        $this->request[] = new SimpleAttachment($key, $content, $filename);
    }
Adds a MIME part to the query. Does nothing for a form encoded packet.

@param string $key          Key to add value to.
@param string $content      Raw data.
@param hash $filename       Original filename.