php验证字符串长度问题

C:\Users\Administrator>php -r "echo strlen('你好')";
4
C:\Users\Administrator>php -r "echo mb_strlen('你好')";
4
C:\Users\Administrator>php -r "echo mb_strlen('你好','utf-8')";
3
C:\Users\Administrator>php -r "echo mb_strlen('你好','gbk')";
2
C:\Users\Administrator>php -r "echo mb_strlen('你好','gb2312')";
2
C:\Users\Administrator>php -r "echo mb_strlen('你好','i')";

 

判断字符串长度并截取：

                if(mb_strlen($val['title'], 'UTF-8')>20){//字符串截取
                    $val['title'] = mb_substr($val['title'], 0, 20, 'UTF-8');
                }