is_null($ var)和($ var === null)有什么区别? [英] What's the difference between is_null($var) and ($var === null)?

问题描述

这之间有什么区别吗...

Is there any difference between this...

if (is_null($var)) {
    do_something();
}

还有这个?

if ($var === null) {
    do_something();
}

检查变量是否包含null时，哪种格式更好?我应该注意哪些极端情况? (我初始化了所有变量，因此不存在的变量不是问题.)

Which form is better when checking whether or not a variable contains null? Are there any edge cases I should be aware of? (I initialize all my variables, so nonexistent variables are not a problem.)

推荐答案

提供了变量已初始化(您确实已指出-尽管我不确定在此情况下这是否重要，但100％不确定.两种解决方案都可能会抛出一个警告(如果未定义变量)，它们在功能上是相同的.我认为===会稍微快一些，尽管它消除了函数调用的开销.

Provided the variable is initialized (which you did indicate - though I'm not 100% sure if this matters in this context or not. Both solutions might throw a warning if the variable wasn't defined), they are functionally the same. I presume === would be marginally faster though as it removes the overhead of a function call.

这实际上取决于您如何看待自己的状况.

It really depends on how you look at your condition.

===用于严格的数据比较. NULL只有一个值"，因此可用于与NULL(这是null值"的PHP常量)进行比较

=== is for a strict data comparison. NULL has only one 'value', so this works for comparing against NULL (which is a PHP constant of the null 'value')

is_null正在检查该变量是否为NULL数据类型.

is_null is checking that the variable is of the NULL data type.

取决于您的选择，真的.

It's up to you which you choose, really.

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