Detect a fetch request in PHP

PHP Snippet 1:

  fetch(url, {
    headers: {
      'credentials': 'same-origin',
      'X-Requested-With': 'XMLHttpRequest',
      'Content-Type': 'application/json'
       // or 'Content-Type': 'application/x-www-form-urlencoded'
    },
    method: 'POST'
  })