Why does accessing array index on boolean value does not raise any kind of error?

问题

When I try to access an array by key which is not exists in this array, php will raise "undefined index" notice error. When I try to do the same on strings, "Illegal string offset " warning is raised. This is an expected behavior and I know how to deal with it.

But when I tried this on boolean or integer values nothing happens:

ini_set('display_errors', 1);
error_reporting(E_ALL);

$var = false;
var_dump($var['test']);

I expect to see some error messages, but $var['test'] just silently sets to NULL.

So why does php permit to access boolean value through an array key without any indication that you are doing something wrong? The hole "access boolean value through an array key" phrase sounds terribly wierd to me, but you can do it in php.

回答1:

It's sad, but it's documented behaviour.

http://php.net/manual/en/language.types.string.php

Note:

Accessing variables of other types (not including arrays or objects implementing the appropriate interfaces) using [] or {} silently returns NULL.

来源：https://stackoverflow.com/questions/25734975/why-does-accessing-array-index-on-boolean-value-does-not-raise-any-kind-of-error