Smarty常用自定义函数扩展实现：中文截取、UBB转HTML与Unescape解码

function smarty_modifier_cn_truncate($string, $strlen = 20, $etc = '...',
    $keep_first_style = false)
{
    $strlen = $strlen*2;
    $string = trim($string);
    if ( strlen($string) <= $strlen ) {
        return $string;
    }
    $str = strip_tags($string);
    $j = 0;
    for($i=0;$i<$strlen;$i++) {
        if(ord(substr($str,$i,1))>0xa0) $j++;
    }
    if($j%2!=0) $strlen++;
    $rstr=substr($str,0,$strlen);
    if (strlen($str)>$strlen ) {$rstr .= $etc;}
    
    // 可选：尝试保留外部样式标签
    if ( $keep_first_style == true && ereg('^<(.*)>$',$string) ) {
        if ( strlen($str) <= $strlen ) {
            return $string;
        }
        $start_pos = strpos($string,substr($str,0,4));
        $end_pos = strpos($string,substr($str,-4));
        $end_pos = $end_pos+4;
        $rstr = substr($string,0,$start_pos) . $rstr . substr($string,$end_pos,strlen($string));
    }
    return $rstr;
}

function smarty_modifier_ubb($str) {
    // 定义各类 UBB 标签到 HTML 的映射规则
    $ubbs['quote'][0] = '/\[quote\](.*?)\[\/quote\]/s';
    $ubbs['quote'][1] = '<blockquote>引用:<hr size=1>\1<hr size=1></blockquote>';
    $ubbs['b'][0] = '/\[b\](.*?)\[\/b\]/s';
    $ubbs['b'][1] = '<b>\1</b>';
    $ubbs['i'][0] = '/\[i\](.*?)\[\/i\]/s';
    $ubbs['i'][1] = '<i>\1</i>';
    // ... (此处省略其他常见标签如u, li, color等映射定义) ...
    $ubbs['img'][0] = '/\[img\](.*?)\[\/img\]/s';
    $ubbs['img'][1] = '<img border="0" src="\1">';
    $ubbs['url'][0] = '/\[url\](.*?)\[\/url\]/s';
    $ubbs['url'][1] = '<a href="\1" target="_blank">\1</a>';
    $ubbs['email'][0] = '/\[email=([^\]]+)\](.*?)\[\/email\]/s';
    $ubbs['email'][1] = '<a href="mailto:\2">\2</a>';
    // ... (更多图片、颜色、字体大小等高级映射逻辑) ...

    // 处理通用列表项符号
    $str = str_replace('[*]','<li>',$str);

    // 依次应用所有正则替换
    foreach ($ubbs as $ubb){
        $str = ubb_replace($ubb[0],$ubb[1],$str);
    }
    return $str;
}

// 辅助函数：执行多次替换直至稳定
function ubb_replace($pattern,$replacement,$str){
    do {
        $str_ret = $str;
        $str = preg_replace($pattern,$replacement,$str);
    }while($$str); // 注意：此处原代码写法可能存在变量语法歧义，建议在实际生产环境中确认变量作用域
    return $str_ret;
}

function smarty_modifier_unescape($str)
{
    $str = rawurldecode($str);
    // 匹配 %uXXXX 格式的 Unicode 或普通字符块
    preg_match_all("/(?:%u.{4})|[^%]+/",$str,$r);
    $ar = $r[0];
    foreach($ar as $k=>$v) {
        // 判断是否为 %u 开头的 6 位字符
        if(substr($v,0,2) == "%u" && strlen($v) == 6)
            // 提取最后4位 hex，打包为 UCS-2 字节流并转为 GB2312
            $ar[$k] = iconv("UCS-2","GB2312",@pack("H4",substr($v,-4)));
    }
    return join("",$ar);
}