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?

score 9 · Accepted Answer · answered Apr 12 '22 at 16:25

9

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 '22 at 16:25

Don't Panic

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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 ? – joachim Jan 31 '23 at 11:28
1

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. – Don't Panic Jan 31 '23 at 16:12

score 0 · Answer 2 · answered Sep 02 '22 at 09:02

0

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 02 '22 at 09:02

the_nuts

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

2 Answers2