PHP的if判断，为什么要写两个条件 - 网络营销电子商务研究中心

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PHP的if判断，为什么要写两个条件

#3 IP: 114.238.140.18

2016-02-28, 10:21 PM

Parrott

初级会员

Join Date: 2008-07-30

Posts: 1

人们在追寻问题的答案的时候，却总是忘记追寻问题本身的意义。
•如果前面的代码已经明确 $str 变量的存在，何必加一句 isset($str) ？
•如果前面的代码不能表明 $str 变量的存在，为什么不加 isset($str) ？

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