Piwik\ProxyHttp::serverStaticFile PHP Method

    public static function serverStaticFile($file, $contentType, $expireFarFutureDays = 100, $byteStart = false, $byteEnd = false, $filename = false)
    {
        // if the file cannot be found return HTTP status code '404'
        if (!file_exists($file)) {
            Common::sendResponseCode(404);
            return;
        }
        $modifiedSince = Http::getModifiedSinceHeader();
        $fileModifiedTime = @filemtime($file);
        $lastModified = gmdate('D, d M Y H:i:s', $fileModifiedTime) . ' GMT';
        // set some HTTP response headers
        self::overrideCacheControlHeaders('public');
        Common::sendHeader('Vary: Accept-Encoding');
        if (false === $filename) {
            $filename = basename($file);
        }
        Common::sendHeader('Content-Disposition: inline; filename=' . $filename);
        if ($expireFarFutureDays) {
            // Required by proxy caches potentially in between the browser and server to cache the request indeed
            Common::sendHeader(self::getExpiresHeaderForFutureDay($expireFarFutureDays));
        }
        // Return 304 if the file has not modified since
        if ($modifiedSince === $lastModified) {
            Common::sendResponseCode(304);
            return;
        }
        // if we have to serve the file, serve it now, either in the clear or compressed
        if ($byteStart === false) {
            $byteStart = 0;
        }
        if ($byteEnd === false) {
            $byteEnd = filesize($file);
        }
        $compressed = false;
        $encoding = '';
        $compressedFileLocation = AssetManager::getInstance()->getAssetDirectory() . '/' . basename($file);
        if (!($byteStart == 0 && $byteEnd == filesize($file))) {
            $compressedFileLocation .= ".{$byteStart}.{$byteEnd}";
        }
        $phpOutputCompressionEnabled = self::isPhpOutputCompressed();
        if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) && !$phpOutputCompressionEnabled) {
            list($encoding, $extension) = self::getCompressionEncodingAcceptedByClient();
            $filegz = $compressedFileLocation . $extension;
            if (self::canCompressInPhp()) {
                if (!empty($encoding)) {
                    // compress the file if it doesn't exist or is newer than the existing cached file, and cache
                    // the compressed result
                    if (self::shouldCompressFile($file, $filegz)) {
                        self::compressFile($file, $filegz, $encoding, $byteStart, $byteEnd);
                    }
                    $compressed = true;
                    $file = $filegz;
                    $byteStart = 0;
                    $byteEnd = filesize($file);
                }
            } else {
                // if a compressed file exists, the file was manually compressed so we just serve that
                if ($extension == '.gz' && !self::shouldCompressFile($file, $filegz)) {
                    $compressed = true;
                    $file = $filegz;
                    $byteStart = 0;
                    $byteEnd = filesize($file);
                }
            }
        }
        Common::sendHeader('Last-Modified: ' . $lastModified);
        if (!$phpOutputCompressionEnabled) {
            Common::sendHeader('Content-Length: ' . ($byteEnd - $byteStart));
        }
        if (!empty($contentType)) {
            Common::sendHeader('Content-Type: ' . $contentType);
        }
        if ($compressed) {
            Common::sendHeader('Content-Encoding: ' . $encoding);
        }
        if (!_readfile($file, $byteStart, $byteEnd)) {
            Common::sendResponseCode(500);
        }
    }

    exit;
}
/**
 * piwik.js proxy
 *
 * @see core/Piwik.php
 */
define('PIWIK_INCLUDE_PATH', '..');
define('PIWIK_DOCUMENT_ROOT', '..');
define('PIWIK_USER_PATH', '..');
require_once PIWIK_INCLUDE_PATH . '/libs/upgradephp/upgrade.php';
// Composer autoloader
if (file_exists(PIWIK_INCLUDE_PATH . '/vendor/autoload.php')) {
    $path = PIWIK_INCLUDE_PATH . '/vendor/autoload.php';
    // Piwik is the main project
} else {
    $path = PIWIK_INCLUDE_PATH . '/../../autoload.php';
    // Piwik is installed as a dependency
}
require $path;
$file = '../piwik.js';
$daysExpireFarFuture = 10;
$byteStart = $byteEnd = false;
if (!defined("PIWIK_KEEP_JS_TRACKER_COMMENT") || !PIWIK_KEEP_JS_TRACKER_COMMENT) {
    $byteStart = 369;
    // length of comment header in bytes
}
$environment = new \Piwik\Application\Environment(null);
$environment->init();
ProxyHttp::serverStaticFile($file, "application/javascript; charset=UTF-8", $daysExpireFarFuture, $byteStart, $byteEnd);
exit;