自己写的php中文截取函数mb_strlen和mb_substr

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("%(?:       [x09x0Ax0Dx20-x7E]           # ASCII     | [xC2-xDF][x80-xBF]            # non-overlong 2-byte     |  xE0[xA0-xBF][x80-xBF]       # excluding overlongs     | [xE1-xECxEExEF][x80-xBF]{2} # straight 3-byte     |  xED[x80-x9F][x80-xBF]       # excluding surrogates     |  xF0[x90-xBF][x80-xBF]{2}    # planes 1-3     | [xF1-xF3][x80-xBF]{3}         # planes 4-15     |  xF4[x80-x8F][x80-xBF]{2}    # plane 16     )%xs",$text,$out);  }else{   return strlen($text);  } }}

/* from Internet, author unknown */if (!function_exists("mb_substr")) {    function mb_substr($str, $start, $len = "", $encoding="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);    }}