PHP CASE语句不适用于零值 [英] PHP CASE statement not working with ZERO values

问题描述

我不明白这里发生了什么.从逻辑上来说，这对我来说没有任何意义.

I don't understand what's happening here. Logically, it doesn't make any sense to me.

<?php
$level = 0;

switch ($level) {

  case $level > 80: $answer = 'high'; break;
  case $level > 60: $answer = 'moderate-to-high'; break;
  case $level > 40: $answer = 'moderate'; break;
  case $level > 20: $answer = 'low-to-moderate'; break;
  default: $answer = 'low'; break;
}   
echo $answer;
?>

当$ level == 0时，它返回高".这对我来说没有任何意义.有人可以解释这里发生了什么吗?

When $level == 0, it returns "high". This doesn't make any sense to me. Can someone explain what's happening here?

推荐答案

将switch ($level)更改为switch (true)，这将起作用.

Change switch ($level) to switch (true) and this will work.

switch 语句对案件. PHP正在评估您的>比较，因此case $level > 80变为case false. false被认为等于0，因此第一种情况匹配.

switch statements perform equality tests on the values in the cases. PHP is evaluating your > comparisons, so case $level > 80 becomes case false. false is considered to be equal to 0, so the first case matches.

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