php：根据中文裁减字符串函数方法

    define(CHARSET, 'UTF-8'); // 系统默认编码    /**     * 根据中文裁减字符串     * @param $string - 字符串     * @param $length - 长度     * @param $doc - 缩略后缀     * @return 返回带省略号被裁减好的字符串     */    function cutstr( $string, $length, $dot = '...' ) {        if ( strlen( $string ) <= $length ) {            return $string;        }        $pre = chr( 1 );        $end = chr( 1 );        $string = str_replace( array( '&', '"', '<', '>' ), array( $pre . '&' . $end, $pre . '"' . $end, $pre . '<' . $end, $pre . '>' . $end ), $string );        $strcut = '';        if ( strtolower( CHARSET ) == 'utf-8' ) {            $n = $tn = $noc = 0;            while ( $n < strlen( $string ) ) {                $t = ord( $string[$n] );                if ( $t == 9 || $t == 10 || (32 <= $t && $t <= 126) ) {                    $tn = 1;                    $n++;                    $noc++;                } elseif ( 194 <= $t && $t <= 223 ) {                    $tn = 2;                    $n += 2;                    $noc += 2;                } elseif ( 224 <= $t && $t <= 239 ) {                    $tn = 3;                    $n += 3;                    $noc += 2;                } elseif ( 240 <= $t && $t <= 247 ) {                    $tn = 4;                    $n += 4;                    $noc += 2;                } elseif ( 248 <= $t && $t <= 251 ) {                    $tn = 5;                    $n += 5;                    $noc += 2;                } elseif ( $t == 252 || $t == 253 ) {                    $tn = 6;                    $n += 6;                    $noc += 2;                } else {                    $n++;                }                if ( $noc >= $length ) {                    break;                }            }            if ( $noc > $length ) {                $n -= $tn;            }            $strcut = substr( $string, 0, $n );        } else {            for ( $i = 0; $i < $length; $i++ ) {                $strcut .= ord( $string[$i] ) > 127 ? $string[$i] . $string[++$i] : $string[$i];            }        }        $strcut = str_replace( array( $pre . '&' . $end, $pre . '"' . $end, $pre . '<' . $end, $pre . '>' . $end ), array( '&', '"', '<', '>' ), $strcut );        $pos = strrpos( $strcut, chr( 1 ) );        if ( $pos !== false ) {            $strcut = substr( $strcut, 0, $pos );        }        return $strcut . $dot;    }