Compile Error: Cannot redeclare Piwik_getUrlTrackPageView()

Hello,
I've downloaded the piwik's api for php few minutes ago, and when i try to create an instance of the tracker, throw this message:

Compile Error: Cannot redeclare Piwik_getUrlTrackPageView() (previously declared in PiwikTracker.php:1224) in PiwikTracker.php line 1228

I dont have any idea of what to do with this issue.