PHP字符串截取，计算字符串长度

 1 /**
 2  * 字符串截取，支持中文和其他编码
 3  * @param  [string]  $str     [字符串]
 4  * @param  integer $start   [起始位置]
 5  * @param  integer $length  [截取长度]
 6  * @param  string  $charset [字符串编码]
 7  * @param  boolean $suffix  [是否有省略号]
 8  * @return [type]           [description]
 9  */
10 function msubstr($str, $start=0, $length=15, $charset="utf-8", $suffix=true) {
11     if(function_exists("mb_substr")) {
12         return mb_substr($str, $start, $length, $charset);
13     } elseif(function_exists('iconv_substr')) {
14         return iconv_substr($str,$start,$length,$charset);
15     }
16     $re['utf-8']   = "/[x01-x7f]|[xc2-xdf][x80-xbf]|[xe0-xef][x80-xbf]{2}|[xf0-xff][x80-xbf]{3}/";
17     $re['gb2312'] = "/[x01-x7f]|[xb0-xf7][xa0-xfe]/";
18     $re['gbk']    = "/[x01-x7f]|[x81-xfe][x40-xfe]/";
19     $re['big5']   = "/[x01-x7f]|[x81-xfe]([x40-x7e]|xa1-xfe])/";
20     preg_match_all($re[$charset], $str, $match);
21     $slice = join("",array_slice($match[0], $start, $length));
22     if($suffix) {
23         return $slice."…";
24     }
25     return $slice;
26 }
27 /**
28  * @计算中文字符串长度，只支持UTF8编码
29  */
30 function utf8_strlen($string = null) {
31        preg_match_all(“/./us”, $string, $match);
32        return count($match[0]);
33 }