Store PHP value in JSON

I was wondering if there was a way to retrieve a value of a php variabile in a JSON file.
For example, I have this following JSON file (file.json):

{
   "Hello": "Hello $name"
}

And this PHP file:

<?php
$name = "Rick";
$jsonFile = json_decode("file.json", true);
$hello = $jsonFile["Hello"];
echo $hello;
?>

What if I want to echo Hello Rick, instead of Hello $name?
Is it impossibile or is there a way to do it?