EXCLAM
唷，咳（书面语中用来表示吃惊、松口气或酷热难耐等）
Phew is used in writing to represent the soft whistling sound that you make when you breathe out quickly, for example when you are relieved or shocked about something or when you are very hot.
例句
Phew, what a relief!
唷，真是大松一口气！