Why am I getting Undefined property: stdClass:: with PHP8 when using the nullsafe operator before an undeclared property?

Question

Php 8.0 introduced the nullsafe operator which can be used like so $foo?->bar?->baz;. I have a code sample running on php 8.1 that throws the error Undefined property: stdClass::$first_name even though it is using the nullsafe operator:

$reference = (object) $reference; // Cast of array to object

return [
    'FirstName' => $reference?->first_name,
];

To solve the error, I have to use the null coalescing operator:

$reference = (object) $reference; // Cast of array to object

return [
    'FirstName' => $reference->first_name ?? null,
];

Why is the nullsafe operator throwing an error in this case?

My rule of thumb on this topic is to always null coalesce at the end and ONLY use the nullsafe operator when chaining methods. — mickmackusa
– mickmackusa ♦, Commented Dec 19, 2024 at 12:07

Don't Panic · Accepted Answer · 2022-04-12 16:25:21Z

17

You seem to have a slight misunderstanding of what the nullsafe operator does.

If $reference was null, then $reference?->first_name would return null with no warning, but since $reference is actually an object, ?-> just functions like a normal object operator, hence the undefined property warning.

answered Apr 12, 2022 at 16:25

Don't Panic

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2 Comments

joachim Over a year ago

So how are you supposed to do it when you have a reference chain where the first object definitely exists? e.g. $exists->maybe->also_maybe ?

Don't Panic Over a year ago

Basically, this operator only comes into play if the the left-hand side is null. If the $exists object is set, but has no maybe property, then $exists->maybe, will produce the same issue the question is asking about where the nullsafe operator isn't really useful. If the maybe property is present, but might have a null value, then the nullsafe operator could be used after it to prevent a warning when trying to read also_maybe, or anything else chained after that. If you don't know whether the first property in the chain exists or not, it's probably better to use ?? instead.

the_nuts · Accepted Answer · 2022-09-02 09:02:43Z

1

You can use a try-catch in case you have many nested properties:

try {
    if ($response->foo->bar->foo->bar->status == 'something') {
        ...
    }
} catch (\ErrorException $ex) {
    // Property missing exception will be caught here
}

answered Sep 2, 2022 at 9:02

the_nuts

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1 Comment

mickmackusa Dec 19, 2024 at 12:11

Writing a try-catch block on every object property access would leave most professional scripts in a horrifically bloated state.

kahatanna7 · Accepted Answer · 2025-04-15 13:15:34Z

1

In your case you will need to check both $reference and $reference->first_name for null. Thus the proper solution would be:

$reference = (object) $reference; // Cast of array to object

return [
    'FirstName' => $reference?->first_name ?? null,
];

answered Apr 15 at 13:15

kahatanna7

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