code: public function add($severity, $content, $filename, $line)
      {
          $content = str_replace('%', '%%', $content);
          $this->testLatestError($severity, $content, $filename, $line);
      }
docs: Adds an error to the front of the queue.
  
  @param int $severity       PHP error code.
  @param string $content         Text of error.
  @param string $filename        File error occoured in.
  @param int $line           Line number of error.