<?php
function ubb2xhtml($ubb) {
    $flash = <<<END
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
 codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0" width="%1\$d" height="%2\$d">
 <param name="movie" value="%3\$s" />
 <param name="quality" value="high" />
 <embed src="%3\$s" width="%1\$d" height="%2\$d" quality="high" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer"></embed>
</object>
END;
    $match = array(
        '%\[url=([^\s]+)\](.*?)\[/url\]%s',
        '%\[email=([^\s])+\](.*?)\[/email\]%i',
        '%\[img width=(\d+) height=(\d+)\](.*?)\[/img\]%s',
        '%\[img=([^\s]+)\/\]%s',
        '%\[flash width=(\d+) height=(\d+)\](.*?)\[/flash\]%se',
        '%\[(b|i|u|strike|sup|sub)\](.*?)\[/\1\]%s',
        '%\[h([1-6])\](.*?)\[/h\1\]%s',
        '%\[hr\/\]%s',
        '%\[color=([^\s]+)\](.*?)\[/color\]%s',
        '%\[font=([^\"]+)\](.*?)\[/font\]%s',
        '%\[size=([^\s]+)\](.*?)\[/size\]%s',
        '%\[align=(center|right|left)\](.*?)\[/align\]%s',
        '%\[valign=(middle|top|bottom)\](.*?)\[/valign\]%s',
        /*
        '%\[ul\](.*?)\[/ul\]%s',
        '%\[ul=(circle|disc|square)\](.*?)\[/ul\]%s',
        '%\[ol\](.*?)\[/ol\]%s',
        '%\[ol type=([aAiI1]) start=([a-zA-Z1-9])\](.*?)\[/ol\]%s',
        '%\[li\](.*?)\[/li\]%s',
        */
        '%\[table=([^\s]+?)\](.*?)\[/table\]%s',
        '%\[caption\](.*?)\[/caption\]%s',
        '%\[tr=([^\s]+?)\](.*?)\[/tr\]%s',
        '%\[th\](.*?)\[/th\]%s',
        '%\[td\](.*?)\[/td\]%s',
        '%\[note\](.*?)\[/note\]%s',
        '%\[quote=(.*?)\](.*?)\[/quote\]%s',
        '%\[code\](.*?)\[/code\]%s',
        '%[ ]{2}%s', // make double-spaces truly double-spaces!
        
    );
    $replace = array(
        '<a href="\1" target="_blank">\2</a>',
        '<a href="mailto:\1" target="_blank">\2</a>',
        '<img src="\3" width="\1" height="\2" border="0" />',
        '<img src="\1" border="0" />',
        'sprintf("$flash", "\1", "\2", "\3")',
        '<\1>\2</\1>',
        '<h\1>\2</h\1>',
        '<hr>\n',
        '<font color="\1">\2</font>',
        '<font face="\1">\2</font>',
        '<font size="\1">\2</font>',
        '<div align="\1">\2</font>',
        '<div valign="\1">\2</font>',
        /*
        '<ul>\1</ul>',
        '<ul type="\1">\2</ul>',
        '<ol>\1</ol>',
        '<ol type="\1" start="\2">\3</ol>',
        '<li>\1</li>',
        */
        "<table class=\"$1\" cellspacing=\"1\">\n$2</table>",
        "\t<caption>$1</caption>\n",
        "\t<tr class=\"$1\">\n$2\t</tr>\n",
        "\t\t<th>$1</th>\n",
        "\t\t<td>$1</td>\n",
        '<div class="note"><span class="hint">发布者备注</span><hr />\1</div>',
        '<div class="quote"><span class="hint">引用</span>(来源: <a href="\1" target="_blank">\1</a>)<br />\2</div>',
        '<span class="hint" style="margin-left: 10px">代码</span><div class="code">\1</div>',
        '&nbsp; ',
    );
    if (preg_match('%\[table=(.*?)\/table\]%s', $ubb, $tablecells)) //如果有表格, 先去除单元格之间的多余空白
    {
        $bb = preg_replace('%\]([\r\n\s]*)\[%si', '][', $tablecells[1]);
        $ubb = str_replace($tablecells[1], $bb, $ubb);
    }
    $html = preg_replace($match, $replace, nl2br(htmlspecialchars($ubb)));
    $html = preg_replace('/<br \/>\s*<(td|th|tr|table|ul|ol|li)/m', "\n" . '<\1', $html);
    return $html;
}

教程地址：http://www.phprm.com/develop/b45e942b9551f8a04056ec1bba79be34.html

欢迎转载！但请带上文章地址^^