\n";
continue;
}
// Lists (ordered/unordered, nested, task items).
if (preg_match('/^(\s*)([-*+]|\d+[.)])(\s+)(.*)$/', $line, $m)) {
$flush();
$out .= md_list($lines, $i, $blocks, $refs, strlen($m[1]), $used);
continue;
}
// Otherwise: paragraph text (indentation trimmed).
$para[] = $trimmed;
}
$flush();
return $out;
}
/**
* Consume a list starting at $lines[$i] whose marker sits at $baseIndent, and
* return its HTML. Advances $i (by reference) to the last consumed line. Each
* item's body is parsed recursively so nested lists and multi-line items work.
*/
function md_list(array $lines, int &$i, array &$blocks, array $refs, int $baseIndent, array &$used): string
{
$n = count($lines);
$marker = '/^(\s*)([-*+]|\d+[.)])(\s+)(.*)$/';
$ordered = null;
$items = []; // Each item: array of its (de-indented) content lines.
$loose = false;
$pendingBlank = false;
while ($i < $n) {
$line = $lines[$i];
if (trim($line) === '') {
$pendingBlank = true;
$i++;
continue;
}
$indent = strlen($line) - strlen(ltrim($line, ' '));
if (preg_match($marker, $line, $m) && strlen($m[1]) <= $baseIndent + 1) {
// A new item at this list's level.
if ($indent > $baseIndent + 1) {
break; // Belongs to a nested list handled by recursion below.
}
if ($ordered === null) {
$ordered = ctype_digit($m[2][0]);
}
if ($pendingBlank && $items) {
$loose = true;
}
$pendingBlank = false;
$content = strlen($m[1]) + strlen($m[2]) + strlen($m[3]);
$items[] = [substr($line, $content)];
$i++;
continue;
}
if ($indent > $baseIndent && $items) {
// Continuation / nested content for the current item.
if ($pendingBlank) {
$loose = true;
$items[count($items) - 1][] = '';
}
$pendingBlank = false;
$strip = min($indent, $baseIndent + 2);
$items[count($items) - 1][] = substr($line, $strip);
$i++;
continue;
}
break; // Dedented non-list line ends the list.
}
$i--; // Step back to the last line that belonged to the list.
$tag = $ordered ? 'ol' : 'ul';
$html = "<$tag>\n";
foreach ($items as $item) {
// Task-list checkbox at the very start of the item.
$task = '';
if (preg_match('/^\[([ xX])\]\s+(.*)$/', $item[0], $tm)) {
$checked = strtolower($tm[1]) === 'x' ? ' checked' : '';
$task = ' ';
$item[0] = $tm[2];
}
$inner = md_blocks($item, $blocks, $refs, $used);
if (!$loose) {
// Tight list: drop the
wrapping the item's leading text, even
// when a nested list or other block follows it.
$inner = preg_replace('#^
(.*?)
(\n|$)#s', '$1$2', $inner);
}
$html .= '
' . $task . rtrim($inner, "\n") . "
\n";
}
return $html . "\n";
}
function markdown_to_html(string $md): string
{
$md = str_replace(["\r\n", "\r"], "\n", $md);
// 1. Pull out fenced code blocks (``` or ~~~) and replace with placeholders.
$blocks = [];
$md = preg_replace_callback('/^[ \t]*(`{3,}|~{3,})([^\n]*)\n(.*?)^[ \t]*\1[ \t]*$/ms', function ($m) use (&$blocks) {
$lang = md_fence_lang(preg_replace('/[^A-Za-z0-9_+#-].*$/', '', trim($m[2])));
$code = rtrim($m[3], "\n");
$html = highlight_code($code, $lang);
// Delimit with \x02 (not \x00): the placeholder sits on its own line and
// is matched later via trim($line), and trim() strips null bytes (\0) by
// default — which would corrupt the key and leak "BLOCKn" into the page.
$key = "\x02BLOCK" . count($blocks) . "\x02";
$blocks[$key] = '