<?php
ini_set('display_errors', 'On');
error_reporting(E_ALL);

$my_text = " a";

use MichelfMarkdown;
$my_html = Markdown::defaultTransform($my_text);

echo "end";

$my_html = MichelfMarkdown::defaultTransform($my_text);

/path/to/
  |- index.php
  `- Michelf/
      |- Markdown.php
      |- MarkdownInterface.php
      `- […]

require_once 'vendor/autoload.php';
use MichelfMarkdown;

$my_text = 'a';
$my_html = Markdown::defaultTransform($my_text);

require_once 'Michelf/Markdown.inc.php';
use MichelfMarkdown;

$my_text = 'a';
$my_html = Markdown::defaultTransform($my_text);

composer require michelf/php-markdown
composer dump-autoload