Bulleted list from dashes

Question

Let's keep this simple.

Input:

- abc
- def
- ghi

Desired output (whitespace optional):

<ul>
    <li>abc</li>
    <li>def</li>
    <li>ghi</li>
</ul>

Current code:

$output = preg_replace_callback(
    "((^- (.*)$\r*\n*)+)m",
    function($m) {
        return "<ul><li>".
            implode(
                "</li><li>",
                preg_split(
                    "(^- )m",
                    substr($m[0],2)
                )
            ).
            "</li></ul>";
    },
    $input
);

It works, the output is exactly what I want, but it seems kinda... hackish. Having a preg_split inside a preg_replace_callback seems a bit redundant, but I can't seem to find a way of capturing subpatterns that are inside a quantifier. If I could do that then I would implode the subpatterns rather than having to split the matched part again.

Any suggestions?

Answer 1

Wouldn't this give you the desired output:

$result = '<ul>' . preg_replace('/^- (.*)$/m', '<li>$1</li>', $subject) . '</ul>';

Update:

$output = preg_replace_callback(
    "((^- (.*)$\r*\n*)+)m",
    function($m) {
        return '<ul>' . preg_replace('/^- (.*)$/m', '<li>$1</li>', $m) . '</ul>';
    },
    $input
);

Answer 2

Another option is to do this in two passes:

1. replace - foo by <li>foo</li> in every line
2. detect blocks of list items and add <ul></ul> around them

The code looks pretty straigtforward to me:

$output_li = preg_replace("/^- (.*)$/m", "<li>$1</li>", $input);
$output = preg_replace("/((<li>.*<\/li>\n)+)/m", "<ul>\n$1</ul>\n", $output_li);

If you want to allow nested lists, you might also want to allow other constructions. Why not use a php port of markdown then? If it's only about nested lists, a way to do that would be to use a recursive descent parser which would call itself whenever there is a new indentation level.