1. /** 
  2.      * 截取字符串（utf-8编码） 
  3.      * 
  4.      * @param string $str   要截取的字符串 
  5.      * @param int $length   截取的长度 
  6.      * @return string 
  7.      */ 
  8.     public function truncate($str) 
        {
            $return = '';
            $length = strlen($str);
            if($length<=6) return $str;
            else{            
                switch($length){
                    case 10:
                    case 9:
                        $length -= 2;
                        break;
                    case 8:
                    case 7:
                        $length -= 1;
                        break;
                   default :
                       $length -= 4;
                }
            }

            for ($i = 0; $i < $length; $i++) {
                $tmp = substr($str, $i, 1);
                if (ord($tmp) > 128) {
                    $setup = 3;
                    $return .= substr($str, $i, $setup);
                    $i+=($setup-1);
                } else {
                    $return .= $tmp;
                }
            }
            return $return;
        }