H2 tag auto ID in php string

I'm trying to write a wordpress filter that autopar开发者_JS百科ses the content and takes the following:

<h2>lesson 1 bannanas</h2>

and replaces it with

<h2 id="lesson-1-bannanas">lesson 1 bannanas</h2>

So that I can then link people directly to sections of a page or blogpost. How would I do this without resorting to something as heavy as DOMDocument?

If you have a coherent input like that, then you can use regular expressions. In this case it's both very acceptable and simple:

$html = preg_replace_callback("#<(h[1-6])>(.*?)</\\1>#", "retitle", $html);

function retitle($match) {
    list($_unused, $h2, $title) = $match;

    $id = strtolower(strtr($title, " .", "--"));

    return "<$h2 id='$id'>$title</$h2>";
}

The id conversion needs a bit more work. And to make the regex more reliable the innter text match pattern (.*?) could be written as ([^<>]*) for example.

I have created a php function to adding id to all h2 tags automatically.

function h2slug($text) {
    preg_match_all("|<h2(.*)>(.*)</[^>]+>|U", $text, $out, PREG_SET_ORDER);
    foreach ($out as $header) {
        $slug = slug($header[2]);
        $header[1] = preg_replace('/(?<!\S\W\w\s)(\s?)id(\s?)="(\w*\W*)"/', '' , $header[1]);
        $text = str_replace($header[0], '<h2 id="'. $slug .'"'. $header[1] .'>'. $header[2] .'</h2>', $text);
    }
    return $text;
}

Using:

<?php echo h2slug('<h2>Lesson 1 bannanas.</h2>'); ?>

Export:

<h2 id="lesson-1-bannanas">Lesson 1 bannanas.</h2>

Another way (that actually is quite simple, although it resorts to dom manipulation) is using jQuery to add a id, thats equal to the content of the h2

You could use str_replace to replace the opening h2 tag with one containing your ID

$tag = '<h2>My content</h2>';
$tag = str_replace('<h2>', '<h2 id = "an id">', $tag);
echo $tag;