Bug: Proper json_last_error() handling with try catch

[Pilskalns]

So, the last release introduces more strict JSON syntax check.

There is an inherent/global issue with how json_last_error() works. In short, the returned error code can be a false positive. It does not reset after a successful encode or decode call. It changes only when there is a new error code.

At the issue core is the following sequence, which gives unintuitive results:

<?php
json_decode("\00invalid json");
var_dump(json_last_error());

json_decode("[]", true, 512, JSON_THROW_ON_ERROR);
var_dump(json_last_error());

Both var dumps would return an error code. You can read about the issue source over this thread: php/php-src#10166

While in isolation this works ok, in the integration it becomes unreliable if, in the same call/request, there was another error code thrown (i.e. to check if a string is a json). I'm preparing a PR that uses try-catch to handle the error properly.