[Bug] Fixed fatal error on PHP5.3 using timer

PHP5.3 does not support calling $this within a closure
Renaming $self to unintuitive var name for consistency
Merge remote-tracking branch 'origin/version-fix'

* origin/version-fix:
  Renaming $self to unintuitive var name for consistency
  [Bug] Fixed fatal error on PHP5.3 using timer
Add libevent timers fix to CHANGELOG