PHP多个三元运算符未按预期工作 [英] PHP multiple ternary operator not working as expected

问题描述

为什么要打印2?

echo true ? 1 : true ? 2 : 3;

据我了解，它应该打印1.

With my understanding, it should print 1.

为什么它不能按预期工作?

Why is it not working as expected?

推荐答案

因为您编写的内容与以下内容相同:

Because what you've written is the same as:

echo (true ? 1 : true) ? 2 : 3;

并且您知道1被评估为true.

and as you know 1 is evaluated to true.

您期望的是:

echo (true) ? 1 : (true ? 2 : 3);

因此，请始终使用大括号来避免此类混淆.

So always use braces to avoid such confusions.

正如已经编写的那样，三元表达式在PHP中保留了关联性.这意味着，首先将在 left 中执行第一个，然后执行第二个，依此类推.

As was already written, ternary expressions are left associative in PHP. This means that at first will be executed the first one from the left, then the second and so on.

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