CodeIgniter Memcached Caching

[eluser]sweetD[/eluser]
It seems the error is coming from here;

Code:

if ($this->_options[self::OPT_COMPRESSION]) {
   $flag = 16;
   $value = gzcompress($value);
  }

which is defined earlier;

Code:

const OPT_COMPRESSION = -1001;

I tried to echo $this->_options[self::OPT_COMPRESSION] and it reproduced the error above, again this is when it's inside of codeigniter, not when it's being used as standalone.