Symptoms
The following error is thrown when trying to provision resource:
Internal Server Error: Trying to get property of non-object at /usr/share/aps/php/aps/2/aps.php:584
Cause
It is an attempt to get a property of an object but the object is empty. For instance the error might be displayed when user wants to get subscription ID by creating a relation to it:
"relations": {
"subscription": {
"type": "http://aps-standard.org/types/core/subscription/1.0",
"collection": false
}
}
and tries to get the id in provision() method:
$subscription_id = $this->subscription->subscriptionId;
But since there is no required: true attribute in resource schema the link was not created automatically so $this->subscription is empty and trying to get 'subscriptionId' property of this object would result in "Trying to get property of non-object" error.
Resolution
There is no general solution for this error, it is needed to add troubleshooting code and verify object existence before trying to use it.