字符串显示为等于数字 [英] String is being shown as equal to a number

问题描述

我的一些php出现了一个奇怪的问题.似乎正在发生的事情是显示0等于字符串"done".这是正在发生的事情:

I'm having a strange problem in some of my php. What seems to be happening is that 0 is being shown as equal to the string "done". Here's what's happening:

if(!isset($pointer)){
    $pointer = 0;   
}
error_log($pointer); //in this instance, I haven't set a pointer, returns 0
if($pointer == "done"){
    die();
}

由于某种原因，第二个if语句将触发并杀死脚本.我不知道为什么，当$ pointer等于0时，它显然也等于"done".这是我所忽略的超级简单的事情吗?

For some reason, the second if statement is triggering and killing the script. I can't figure out why, when $pointer is equal to 0, it is apparently also equal to "done". Is this something super easy that I'm just overlooking?

我已经解决了这种情况，在第二个if语句上使用===给了我想要的结果，我只是想了解为什么它首先没有起作用.谢谢您的时间.

I've worked around the situation, using === on the second if statement gives me the desired result, I would just like to understand why it wasn't working in the first place. Thank you for your time.

推荐答案

这是类型比较问题；如您所说，使用:

It's a type comparison issue; as you say, using:

if($pointer === "done"){

强制检查值和类型.

正在发生的情况是，完成"被转换为数字以进行比较.由于那里没有数字，因此它为空.在比较中，null的值为0.

What is happening is that 'done' is being converted into a number for the comparison. Since there are no numbers in there, it's coming out as null. And null evaluates to 0 in your comparison.

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