AJAX sending data in GET request is not working

I have an AJAX function running from my frontend looking like this:

//api.js

function getTransactions(authToken) {
  $.ajax({
    type: 'GET',
    data: {
      'authToken':
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
    },
    crossDomain: true,
    dataType: 'JSON',
    url: 'http://localhost:8000/transactions',
  }).done(function (data) {
.....

I have been trying to pass the authToken parameter to the data object, and then retrieve it in the PHP backend using (case transactions):

//index.php

$request = $_SERVER["REQUEST_URI"];

switch ($request) {
  case "/login" :
    require __DIR__ . "/login.php";
    $userEmail = $_POST["userEmail"];
    $userPassword = $_POST["userPassword"];
    echo login($userEmail, $userPassword);
    break;
  case "/transactions" :
    require __DIR__ . "/transactions.php";
    $authToken = $_GET["authToken"];
    getTransactions($authToken);
    break;
}

If I hardcode the authToken into the getTransactions function inside case "/transactions", it works fine.

But there’s something, either in the $_GET() in index.php, or in the AJAX function that it preventing the data from getting into the getTransactions function in index.php.

I have tried putting strings around the authToken key in the data object, also using the authToken parameter, as well as JSON.stringify-ing the data object. Further, I have changed/removed the dataType, and exhausted every other method suggested by stack overflow and other websites.

This is especially difficult because it’s my first time using PHP, and I don’t know how to show echos in my terminal, so I can’t see any output from the PHP files.

Any help would be appreciated.