Using PHP 5.3 or 5.4 will generate (tons of) log entries for invalid static access of non-static properties for GA_Filter.
Quick fix: all methods of GA_Filter are *only* used in static context and should be declared with
Some minor issues:
plugin_dir_path( __FILE__ ) does add a trailing slash. Not needed to do so twice.
$gaf = new GA_Filter(); is not used by the plugin.
There is no need for it, as the interface is static already.
For consistence either omit all
public function or always use it.
If time permits I'll add a more complete coding review later this year (basic consistency, common error and performance checkup. maybe something about missing source documentation too).