Sending Data in JSON Format in PHP

When a website is running, it often happens that some URLs return not HTML code, but JSON. Let's write an example of such a page:

test.php<?php
  $data = [1, 2, 3];
  $json = json_encode($data);
  echo $json;
?>

A more correct approach would be to send the appropriate HTTP header as well:

test.php<?php
  $data = [1, 2, 3];
  $json = json_encode($data);
  
  header('Content-Type: application/json');
  echo $json;
?>