Notice: Unknown: file created in the system's temporary directory in Unknown on line 0

This is not an error, this is a notice. See this request. Basically, it's just telling you that it has fallen back to the system's default temp dir, as opposed to something more specific that you have provided. You can override it to something more specific (like a temp dir specifically for this app) or disable notices via error_reporting(). I'd recommend the former.

Be sure that the directory you want to save something is writeable.

For example, in my case, it was a Concrete 5 directory that has to be writeable. After I change permission to 777 it stopped crying.