code: public function addFree(ProcessDetails $processDetails) {
  		$pid = $processDetails->getPid();
  		$this->processDetails[$pid] = $processDetails;
  		$this->sockets[$pid] = $processDetails->getSocket();
  		$this->registerFreeProcess($processDetails);
  		return $this;
  	}
docs: Adds the ProcessDetails to the list and registers it as a free one.
  
  @param ProcessDetails $processDetails
  @return ProcessDetailsCollection