Home Backend Development PHP Tutorial 一个基础有关问题,多谢

一个基础有关问题,多谢

Jun 13, 2016 am 10:35 AM
echo false null quot true

一个基础问题,谢谢。
echo NULL == false?"true":"false"; //输出true
echo false == '0'?"true":"false"; //输出true

为什么下面会输出false呢?
echo NULL == '0'?"true":"false"; //输出false


PHP中变量是以C语言的结构体来存储的,空字符串和NULL,false都是以值为0存储的。
上面这句话是不是正确的。

------解决方案--------------------
php是种弱类型的语言.
所以当你修改成
echo false == 0?"true":"false"; //输出true

也是成立的,所以不能仅仅靠判断'0'就说他是字符串类型因为你使用的是== 
他并不会进行类型比较

如果你要判断字符串的0 应该是 
echo false === '0'?"true":"false"; //输出false

探讨

false是字符串吗?
为什么echo false == '0'?"true":"false"; //输出true

引用:

'0'是一个字符串了,要是null == ""才会是true。

------解决方案--------------------
来,和我一起读手册....
http://ca.php.net/manual/en/language.operators.comparison.php
中间Comparison with Various Types表格....

不同类型变量比较,首先要做类型转换,怎么转换就决定了最终的结果....


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