I tried executing the example code in the README as is, but it did not work.

[OHMORIYUSUKE]

The README example had the following code.

$Parsedown = new Parsedown();

echo $Parsedown->text('Hello _Parsedown_!'); # prints: <p>Hello <em>Parsedown</em>!</p>

But this code gives me an error.
Parsedown must be loaded using autoload for it to run properly.

<?php
require_once __DIR__ . '/vendor/autoload.php';

$Parsedown = new Parsedown();

echo $Parsedown->text('Hello _Parsedown_!'); # prints: <p>Hello <em>Parsedown</em>!</p>

Could you please change the example to the code above?

[0xWDG]

require 'parsedown.php'; is enough to require it in your current php file.