You did not provide that information, so I have to guess a little bit: You are using PHP 5.4 and zlib.output_compression is on on your server?
Then you just stumbled upon bug #18525. Possible solutions:
- Disable
zlib.output_compression. - Apply the patch provided there and report back on that ticket if it works.
- Disable notices.
What you can do when you decide to release the plugin to the public is another issue …