www-lib-markdown/playgroundapi.php

<?php
if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
	http_response_code(405); // method not allowed
	exit();
}

$readerNames = $_POST['readers'];
$markdown = $_POST['markdown'];

$permittedReaders = [
	'MDUnderlinedHeadingReader' => true,
	'MDHashHeadingReader' => true,
	'MDSubtextReader' => true,
	'MDBlockQuoteReader' => true,
	'MDUnorderedListReader' => true,
	'MDOrderedListReader' => true,
	'MDFencedCodeBlockReader' => true,
	'MDIndentedCodeBlockReader' => true,
	'MDHorizontalRuleReader' => true,
	'MDTableReader' => true,
	'MDDefinitionListReader' => true,
	'MDFootnoteReader' => true,
	'MDAbbreviationReader' => true,
	'MDParagraphReader' => true,

	'MDEmphasisReader' => true,
	'MDStrongReader' => true,
	'MDStrikethroughReader' => true,
	'MDUnderlineReader' => true,
	'MDHighlightReader' => true,
	'MDCodeSpanReader' => true,
	'MDSubscriptReader' => true,
	'MDSuperscriptReader' => true,
	'MDLinkReader' => true,
	'MDReferencedLinkReader' => true,
	'MDImageReader' => true,
	'MDReferencedImageReader' => true,
	'MDLineBreakReader' => true,
	'MDHTMLTagReader' => true,
	'MDModifierReader' => true,
];

include 'php/markdown.php';
$readers = [];
foreach ($readerNames as $readerName) {
	if ($permittedReaders[$readerName] ?? false) {
		$ref = new ReflectionClass($readerName);
		$reader = $ref->newInstanceArgs([]);
		array_push($readers, $reader);
	}
}
$parser = new Markdown($readers);
$html = $parser->toHTML($markdown);
header('Content-Type: text/html');
print($html);
?>