Piwik\Plugins\CustomPiwikJs\File::save PHP Method

    public function save($content)
    {
        if (false === file_put_contents($this->file, $content)) {
            throw new AccessDeniedException(sprintf("Could not write to %s", $this->file));
        }
    }

 public function update()
 {
     if (!$this->toFile->hasWriteAccess() || !$this->fromFile->hasReadAccess()) {
         return;
     }
     $newContent = $this->getUpdatedTrackerFileContent();
     if ($newContent !== $this->getCurrentTrackerFileContent()) {
         $this->toFile->save($newContent);
     }
 }