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 variable.

$value = $var['key']

This doesn't throw an error, my intuition is that it would though. What instead happens is that $value is now also null. Is there a particular reason that the above line doesn't throw an error?

If I'm correct, trying to read a non-existing value of an array *does* throw an error. Do you have `error_reporting()` set to `-1`? — MC Emperor, Sep 18 '15 at 10:53
It doesn't throw an error, it would normally raise a notice, but that doesn't appear to be the case with `null`. — Jonnix, Sep 18 '15 at 10:55

score 9 · Accepted Answer · edited May 23 '17 at 11:51

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.

score 0 · Answer 2 · answered Sep 18 '15 at 11:19

You can use this kind of fallback

function _get($from, $key)
{
    if(is_null($from))
    {
        trigger_error('Trying to get value of null');
        return null;
    }
    return $from[$key];
}

Change

$value = $var['key'];

to

$value = _get($var, 'key');

Key of null variable equals null not error

2 Answers2

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