为什么PHP认为0等于字符串? [英] Why does PHP consider 0 to be equal to a string?

问题描述

我有以下代码:

$item['price'] = 0;
/* Code to get item information goes in here */
if($item['price'] == 'e') {
    $item['price'] = -1;
}

它旨在将物料价格初始化为0，然后获取有关其的信息.如果价格被告知为"e"，则表示交换而不是卖出，后者以负数存储在数据库中.

It is intended to initialize the item price to 0 and then get information about it. If the price is informed as 'e' it means an exchange instead of a sell, which is stored in a database as a negative number.

也有可能将价格保留为0，这是因为该项目是奖励商品，或者是因为价格将在以后设置.

There is also the possibility to leave the price as 0, either because the item is a bonus or because the price will be set in a later moment.

但是，每当未设置价格时，将其保留为初始值0，则上述if循环的计算结果为true，并且价格设置为-1.也就是说，它认为0等于"e".

But, whenever the price is not set, which leaves it with the initial value of 0, the if loop indicated above evaluates as true and the price is set to -1. That is, it considers 0 as equal to 'e'.

这怎么解释?

当价格为0(初始化后)时，该行为是不稳定的:有时if的评估结果为true，有时它的评估结果为false.*

When the price is provided as 0 (after initialization), the behavior is erratic: sometimes the if evaluates as true, sometimes it evaluates as false.*

推荐答案

您正在做==，它会为您分类类型.

You are doing == which sorts out the types for you.

0是一个整数，因此在这种情况下它将把'e'强制转换为一个整数.不可解析为1，它将变为0.字符串'0e'将变为0并且匹配！

0 is an int, so in this case it is going to cast 'e' to an int. Which is not parsable as one and will become 0. A string '0e' would become 0 and would match!

使用===

这篇关于为什么PHP认为0等于字符串?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！