在 PHP 中使用 === 比较而不是 == 比较
有没有办法让下面的代码仍然使用开关并返回 b 而不是 a?谢谢！
Is there anyway to make it so that the following code still uses a switch and returns b not a? Thanks!
$var = 0;
switch($var) {
case NULL : return 'a'; break;
default : return 'b'; break;
}
当然，使用 if 语句，你会这样做:
Using if statements, of course, you'd do it like this:
$var = 0;
if($var === NULL) return 'a';
else return 'b';
但对于更复杂的示例，这会变得冗长.
But for more complex examples, this becomes verbose.
推荐答案
抱歉，您不能在 switch 语句中使用 === 比较，因为根据 switch() 文档:
Sorry, you cannot use a === comparison in a switch statement, since according to the switch() documentation:
请注意，switch/case 的比较比较松散.
Note that switch/case does loose comparison.
这意味着您必须想出一个解决方法.来自松散比较表，您可以通过类型转换来利用 NULL == "0" 为 false 的事实:
This means you'll have to come up with a workaround. From the loose comparisons table, you could make use of the fact that NULL == "0" is false by type casting:
<?php
$var = 0;
switch((string)$var)
{
case "" : echo 'a'; break; // This tests for NULL or empty string
default : echo 'b'; break; // Everything else, including zero
}
// Output: 'b'
?>
现场演示
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