Cant get app.txt to generate?

I cant get the app.txt file to show up on my file tree. After I ran the code below not even my echo statement shows up. However when I comment out //$log->addWarning('Foo'); my echo statement shows up but still no app.txt file.

I have read previous questions and have tried restarting my browser and workspace, clearing cache, making a new index.php file but still having no luck. I'm not sure what I am doing wrong here.

Here is my code:

<?php

require 'vendor/autoload.php';

$log = new Monolog\Logger('name'); $log->pushHandler(new Monolog\Handler\StreamHandler('app.txt', Monolog\Logger::WARNING));

$log->addWarning('Foo');

echo 'Hi Mate!';