json_decode return internal 500 in laravel 5.3

i am getting data with curl from an api, this is the original response: {"_items": [{"_id": "58748b586ef49a1b112fb60e", "code": "35", "_etag": "06f6bb57ca650d96fe474d72c40868a90ab13e46", "city": "izmir", "_updated": "2017-01-10 07:20:56", "_links": {"self": {"href": "city/58748b586ef49a1b112fb60e", "title": "city"}}, "_created": "2017-01-10 07:20:56"}], "_links": {"self": {"href": "city", "title": "city"}, "parent": {"href": "/", "title": "home"}}, "_meta": {"max_results": 25, "page": 1, "total": 1}}

which is inside $result variable. when i'm trying to json_decode($result) or when i'm trying $result->_items i got 500 internal error and there is no log record in laravel.log