Ajax之外的变量

I uploaded a json file using Ajax (with vanilla JS).

{
  "list": [
    {"name": "Egzekutor", "date": "19.04.2017, 12:32:57"},
    ...
  ]
}

Now, using addEventListenera, I can change "date" for the current one. Everything works, but I want to save changes in a file. The problem is when I try to use a variable with JSON.stringify(list) in PHP file, because my variable is not seen outside Ajax part. What can I do to use this variable?