code: public static function writeFile($file, $content)
      {
          $handle = fopen($file, 'w');
          if (!self::lockFile($handle, LOCK_EX | LOCK_NB)) {
              $exception = array(
                  "message" => 'exception_file_cannot_be_locked_for_writing',
                  "parameters" => array(
                      "%file%" => basename($file),
                  )
              );
              throw new RuntimeException(json_encode($exception));
          }
          if (fwrite($handle, $content) === false) {
              $exception = array(
                  "message" => 'exception_file_cannot_be_written',
                  "parameters" => array(
                      "%file%" => basename($file),
                  )
              );
              throw new RuntimeException(json_encode($exception));
          }
          self::unlockFile($handle);
      }
docs: Locks and write a file to the filesystem
  
  @param string $file
  @param string $content