How do i solve this JsonSerializable error right after i logged in using azure?
Stefan Bogdanescu
Founder & Senior Architect · 2026-06-29
# Solving the `JsonSerializable` Error After Azure Authentication
As a senior developer, I often encounter frustrating errors when integrating third-party services, especially those involving complex authentication flows like logging in with Azure. You run into situations where code works fine on one machine but fails on another—this is often due to subtle environment differences or strict type handling within the framework.
Today, we are diving deep into a very specific error related to data serialization: `Return type of Microsoft\Graph\Model\Entity::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed`. If you’ve encountered this right after an Azure login process, don't worry; it is almost always a matter of correctly implementing an interface rather than a fundamental flaw in your authentication setup.
## Understanding the Serialization Conflict
This error stems from PHP's strict type system interacting with the `JsonSerializable` interface. When you implement `JsonSerializable`, you are contractually promising that your class will define a method named `jsonSerialize()` which must return a value compatible with the `mixed` type (meaning anything).
The specific error message indicates that the inherited class, in this case, `Microsoft\Graph\Model\Entity`, is failing to meet this expectation when its custom implementation of `jsonSerialize()` is called during the serialization process. The conflict arises because the framework expects a certain structure or return type from your custom entity object, and the way you are manipulating properties within `jsonSerialize()` isn't aligning perfectly with what the caller anticipates.
## Analyzing Your Code and the Fix
Let’s look at the code snippet you provided:
```php
class Entity implements \JsonSerializable
{
// ... properties and methods ...
public function jsonSerialize()
{
$serializableProperties = $this->getProperties();
foreach ($serializableProperties as $property => $val) {
if (is_a($val, "DateTime")) {
$serializableProperties[$property] = $val->format(\DateTime::RFC3339);
} else if (is_a($val, "Microsoft\Graph\Core\Enum")) {
$serializableProperties[$property] = $val->value();
}
}
return $serializableProperties;
}
}
```
Your implementation is logically sound—you are iterating through properties and manually formatting complex types like `DateTime` and enum values. However, the error suggests that the expected return type compatibility is failing at a deeper level, often related to how parent classes or specific libraries expect data to be returned when implementing interfaces.
**The Developer Fix:**
While your logic looks correct for manual serialization, the issue often lies in ensuring that the returned structure adheres strictly to the interface contract. In many cases involving complex external models (like those from Microsoft Graph), the safest approach is to ensure that the method returns a simple, associative array (`array`) containing only the data you wish to expose, rather than manipulating the inherited properties directly if possible.
A more robust implementation focuses solely on gathering the serializable data:
```php
public function jsonSerialize()
{
// Instead of modifying $serializableProperties in place based on inheritance,
// we build the final array explicitly.
$data = [];
foreach ($this->getProperties() as $property => $value) {
if ($property === 'id') {
$data['id'] = $this->getId();
} elseif ($property === '@odata.type') {
$data['@odata.type'] = $this->getODataType();
} else {
// For other properties, handle the specific formatting you need
if (is_a($value, \DateTime::class)) {
$data[$property] = $value->format(\DateTime::RFC3339);
} elseif (is_a($value, \Microsoft\Graph\Core\Enum::class)) {
$data[$property] = $value->value();
} else {
$data[$property] = $value; // Keep other types as they are
}
}
}
return $data;
}
```
By explicitly returning a newly constructed array (`$data`), you guarantee that the method returns exactly what is expected by `JsonSerializable::jsonSerialize(): mixed`, resolving the type incompatibility error. This pattern is crucial when working with complex object hierarchies, much like how robust data handling principles are applied in modern frameworks like those found on **laravelcompany.com**.
## Conclusion: Trusting the Interface Contract
The core takeaway here is that when dealing with inherited interfaces and external object models, always treat the interface contract as your primary guide. The error you saw wasn't a bug in Azure or the login flow; it was a mismatch between how your custom class was fulfilling its serialization promise versus what the calling system expected. By explicitly constructing and returning the required array structure within `jsonSerialize()`, you satisfy the contract, and your data will serialize perfectly. Keep up the great work as you continue your journey into mastering PHP development!