众所周知，php 自带的 strlen 与 substr 函数没法处理中文字符，于是，我们会用 mb_ 系列函数替代。但是，没有 mbstring 库怎么办？这就需要我们自己写一个来替代了，废话不多说，先上代码:

复制代码 代码如下:
if ( !function_exists('mb_strlen') ) {
 function mb_strlen ($text, $encode) {
  if ($encode=='UTF-8') {
   return preg_match_all('%("UTF-8"){
        $limit = strlen($str);
 
        for ($s = 0; $start > 0;--$start) {// found the real start
            if ($s >= $limit)
                break;
 
            if ($str[$s] <= "\x7F")
                ++$s;
            else {
                ++$s; // skip length
 
                while ($str[$s] >= "\x80" && $str[$s] <= "\xBF")
                    ++$s;
            }
        }
 
        if ($len == '')
            return substr($str, $s);
        else
            for ($e = $s; $len > 0; --$len) {//found the real end
                if ($e >= $limit)
                    break;
 
                if ($str[$e] <= "\x7F")
                    ++$e;
                else {
                    ++$e;//skip length
 
                    while ($str[$e] >= "\x80" && $str[$e] <= "\xBF" && $e < $limit)
                        ++$e;
                }
            }
 
        return substr($str, $s, $e - $s);
    }
}