protected function saveCompiledFile($filename)
    {
        $file = PhpFile::instance($filename);

        // Attempt to lock the file for writing.
        try {
            $file->lock(false);
        } catch (\Exception $e) {
            // Another process has locked the file; we will check this in a bit.
        }

        if ($file->locked() === false) {
            // File was already locked by another process.
            return;
        }

        $cache = [
            '@class' => \get_class($this),
            'timestamp' => time(),
            'checksum' => $this->checksum(),
            'files' => $this->files,
            'data' => $this->getState()
        ];

        $file->save($cache);
        $file->unlock();
        $file->free();

        $this->modified();
    }