# 常用函數 empty isset isnull 比較

[![image-1637654833415.png](https://bookstack.treemanou.com/uploads/images/gallery/2021-11/scaled-1680-/S9se8GNFeJJkm3lm-image-1637654833415.png)](https://bookstack.treemanou.com/uploads/images/gallery/2021-11/S9se8GNFeJJkm3lm-image-1637654833415.png)