json_encode only works with JSON_PARTIAL_OUTPUT_ON_ERROR for Model with custom toArray

Question

I have an Eloquent Model, for which I created a custom toArray()-method, to include fields from a meta table (which I get by using the eloquent-meta plugin):

class User extends Model{
 // ... Other stuff
 public function toArray(){
 return array_merge(parent::toArray(), $this->getAllMeta()->toArray());
 }
}

When I now try to send this model as a JSON response using Response::json(...), I get:

UnexpectedValueException in Response.php line 403: The Response content must be a string or object implementing __toString(), "boolean" given.

I have traced the error to the JsonResponse.setData($data)-method, in which the json_encode-call returns false. The json_last_error()-method returns JSON_ERROR_SYNTAX and the json_last_error_msg()-method returns Syntax error.

Using the debugger I stopped on the line below and evaluated the statement myself. As expected, it does not work, however if I call it like this, it works:

json_encode($data, JSON_PARTIAL_OUTPUT_ON_ERROR);

This returns the complete, valid JSON that I expect, without any missing or NULL values.

What's even stranger is, if I stop in the toArray()-method and supply the merged array to json_encode, it works fine, even without partial.

Am I overlooking something obvious here??

• Josh from Qaribou: So Model already implements JsonSerializable, and the jsonSerialize() is just a simple wrapper around its toArray(). Are you supplying the merged array directly, or are you doing json_encode($mymodel->toArray())?
• Lukas Knuth: @JoshfromQaribou no, I'm supplying the model directly. The funny part is, that it works fine, if I remove the toArray()-method.

Answer 1

The problem was with the eloquent-meta plugin I used. Here's the relevant part from my issue:

I traced the error back to the Helpers.maybeDecode($value)-method:

The current implementation tries to parse the value with json_decode($value) and checks, whether that worked, by checking the json_last_error()-function. The problem is, that this doesn't reset the last error.

When the Helpers.maybeDecode($value)-method is called, while Laravel is encoding the model, and the value it tried to decode was not an valid json (for example, a simple string), the error code is set, causing the json_encode()-function to see it and return null. The problem is with the global nature of the error-variable.

My proposed workaround for this is to reset the json_last_error()-function after checking if decoing worked, and the only way I have found to do this is by decoding something valid (even if it's just an empty array).

Here is the Pull Request with the fix.