Is piwik.js parsed for PHP?

Does the /piwik/piwik.js file need to be parsed for PHP?

Is there a way to find out if piwik.js is being executed or if all of my stats come from piwik.php?

piwik.js is served directly by the web server.

piwik.php handles the tracking request from the browser.

js/index.php is a proxy for the above

When is js/index.php called? I can’t find it in the Javascript snippet, piwik.js, or piwik.php.