[基础](%E5%9F%BA%E7%A1%80.md) [预定义变量](%E9%A2%84%E5%AE%9A%E4%B9%89%E5%8F%98%E9%87%8F.md) [变量范围](%E5%8F%98%E9%87%8F%E8%8C%83%E5%9B%B4.md) [可变变量](%E5%8F%AF%E5%8F%98%E5%8F%98%E9%87%8F.md) [来自PHP之外的变量](%E6%9D%A5%E8%87%AAPHP%E4%B9%8B%E5%A4%96%E7%9A%84%E5%8F%98%E9%87%8F.md)