url_to_html

function urltohtml($text)
{
    return preg_replace_callback('/((http|https|ftp|ftps)\:\/\/[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(\/\S*)?)/', 'callback_linker', $text);
}

function callback_linker($text)
{
    $lastchar = substr($text[0], -1, 1);
    if(preg_match('/[^a-zA-Z0-9]/', $lastchar))
    {
        $href = substr($text[0], 0, -1);
        $append = $lastchar;
    }
    else
    {
        $href = $text[0];
        $append = '';
    }
    return "<a href=\"$href\">$href</a>$append";
}