PHP类型变戏法，“字符串" == 0且"String"为==真 [英] PHP type juggling, "String" == 0 and "String" == true

问题描述

我有一个非常简单的问题.在PHP中，

I have a very simple question. In PHP,

if ('abc' == 0){
    //true
}
if ('abc' == 1){
    //false
}

我知道此页面告诉我们，该页面应该像那样.但是，我觉得很奇怪.另外，

I know that this page tell us that it is supposed to be like that. But, I find it wierd. In addition,

if ('abc' == true){
    //true
}
if ('abc' == false){
    //false
}

这两次转换背后的逻辑是什么?

What is the logic behind theses two conversions?

推荐答案

转化1

进行字符串和整数比较时，首先将字符串转换为整数，然后进行比较.由于这些字符串中没有前导整数，因此它们将转换为零.

When string and integer comparisons are made, the string is converted to an integer first and then the comparison is made. Since there are no leading integers in those strings they convert to zero.

转化2

任何非空字符串值都是布尔值true.

Any non-empty string values are boolean true.

从手册:

The following things are considered to be empty:

"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
$var; (a variable declared, but without a value)

另请参见:类型比较

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