Key of null variable equals null not error

Question

We\'ve got variable that for some reason we think would be an array, but it happens to be null.

$var = null

We try to get a value from this var

Answer 1

There is "almost duplicate": Why does accessing array index on boolean value does not raise any kind of error?

the code there looks like:

$var = false;
$value = $var['key'];

and the answer is - it's just document

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

So in this string (I am talking about your case, $var = null, but with boolean would be the same explanation, just replace NULL to boolean)

$var['key']

$var is the variable of type NULL, and accessing variable of type NULL (other type that array or object) using [] silently returns NULL.