Writing JSON data to a JSON file - json

Question

Hello in my application I am currently trying to create my own custom log files in .json format. Reason for this is because I want a well structured and accurate log file which can be easily read and would not depend on some special code in my application to read the data.
I have been able to create a json file: activities.json
I have been able to write and append to that file using File::append($path, $json)
This is a sample of the file contents:
{"controller":"TestController","function":"testFunction()","model":"Test","user":"Kayla","description":"Something happened!! Saving some JSON data here!","date":"2016-06-15"}
{"controller":"TestController","function":"testFunction()","model":"Test","user":"Jason","description":"Something happened!! Saving some JSON data here!","date":"2016-06-15"}
{"controller":"UserController","function":"userFunction()","model":"User","user":"Jason","description":"Another event occurred","date":"2016-06-15"}
Now my issue is the above is not a valid JSON. How do I get it in this format:
[
{"controller":"TestController","function":"testFunction()","model":"Test","user":"Kayla","description":"Something happened!! Saving some JSON data here!","date":"2016-06-15"},
{"controller":"TestController","function":"testFunction()","model":"Test","user":"Jason","description":"Something happened!! Saving some JSON data here!","date":"2016-06-15"},
{"controller":"UserController","function":"userFunction()","model":"User","user":"Jason","description":"Another event occurred","date":"2016-06-15"}
]
Is there a way of writing and appending to a json file in laravel? As much as possible I want to avoid reading the entire file before the append and doing a search and replace since the file may contain hundreds to thousands of records.
I will not use the default Laravel Log function.