Why am I getting Undefined property: stdClass:: with php 8 nullsafe operator

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?

Shurwood

I ran into the same issue today, so you're not the only one that was confused by this – Pops

Answer 1

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.

Harday

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 ? – Doublequick

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. – Tephrite

Answer 2

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
}

Omsk