fWriteCallback = \is_callable($fWriteCallback) ? $fWriteCallback : null; $this->fClearCallback = \is_callable($fClearCallback) ? $fClearCallback : null; } protected function writeImplementation($mDesc) : bool { if ($this->fWriteCallback) { ($this->fWriteCallback)($mDesc); } return true; } protected function clearImplementation() : bool { if ($this->fClearCallback) { ($this->fClearCallback)(); } return true; } }