Quick and dirty way to get all HTML/XML tags in a string

get_unique_tags.php

<?php

function get_unique_tags($data) {
    preg_match_all('/<([^>]+)>/i', $data, $matches);

    $matches = $matches[1];

    foreach ($matches as $i => $match) {
        $matches[$i] = trim($match, '/');
    }

    $matches = array_unique($matches);
    return $matches;
}

$data = '<foo>lorem ipsum</foo><p>lorem ipsum</p>';
var_dump(get_unique_tags($data));