Php Receive Unquote Json String From Js

I'm new to php,JSON, and js. My problem is my php has somehow receive unquote json string from js. I already print the json string after passing it through the function JSON.string

Solution 1:

As mention by @phil, it seem that the reason i got unquote string is because i try to save into file using the execution operator+ using echo. I should used file_put_contents to save the input receive, to preserve the format.