Short PHP code highlighting function

gistfile1.php

function php_highlight($source, $classes = true) {
    $r1 = $r2 = '##';

    // adds required PHP tags (at least with vers. 5.0.5 this is required)
    if (strpos($source, ' ?>') === false) // xml is not THAT important ;-)
    {
        $source = "<?php " . $source . " ?>";
        $r1 = '#&lt;\?.*?(php)?.*?&nbsp;#s';
        $r2 = '#\?&gt;#s';
    }
    elseif (strpos($source, '<? ') !== false)
    {
        $r1 = '--';
        $source = str_replace('<? ', '<?php ', $source);
    }

    $source = highlight_string($source, true);

    if ($r1 == '--') $source = preg_replace('#(&lt;\?.*?)(php)?(.*?&nbsp;)#s', '\\1\\3', $source);

    $source = preg_replace (array ( '/.*<code>\s*<span style="color: #000000">/',    //
                                    '#</span>\s*</code>#',                          //  <code><span black>
                                    $r1, $r2,                 // php tags
                                    '/<span[^>]*><\/span>/'   // empty spans
                                  ),'',$source);

    if ($classes) $source = str_replace(
        array('style="color: #0000BB"', 'style="color: #007700"',
            'style="color: #DD0000"', 'style="color: #FF8000"'),

        array('class="default"', 'class="keyword"',
            'class="string"', 'class="comment"',), $source);
    return $source;
}