Intercept Chinese string PHP code

/**
*
* Chinese string interception
* @param string $string
* @param int $sublen
* @param int $start
* @param string $code
*/
function substr_zh ( $string, $sublen, $start = 0, $code = 'UTF-8' )
{
    if ( $code == 'UTF-8' )
    {
        $pa = "/[x01-x7f]|[xc2-xdf][x80-xbf]|xe0[xa0-xbf][x80-xbf]|[xe1-xef][x80-xbf][x80-xbf]|xf0[x90-xbf][x80-xbf][x80-xbf]|[xf1-xf7][x80-xbf][x80-xbf][x80-xbf]/";
        preg_match_all ( $pa, $string, $t_string );

        if ( count ( $t_string[0] ) - $start > $sublen ) return join ( '', array_slice ( $t_string[0], $start, $sublen ) ) . "...";
        return join ( '', array_slice ( $t_string[0], $start, $sublen ) );
    }
    else
    {
        $start = $start * 2;
        $sublen = $sublen * 2;
        $strlen = strlen ( $string );
        $tmpstr = '';

        for ( $i = 0; $i < $strlen; $i ++ )
        {
            if ( $i >= $start && $i < ( $start + $sublen ) )
            {
                if ( ord ( substr ( $string, $i, 1 ) ) > 129 )
                {
                    $tmpstr .= substr ( $string, $i, 2 );
                }
                else
                {
                    $tmpstr .= substr ( $string, $i, 1 );
                }
            }
            if ( ord ( substr ( $string, $i, 1 ) ) > 129 ) $i ++;
        }
        if ( strlen ( $tmpstr ) < $strlen ) $tmpstr .= "...";
        return $tmpstr;
    }
}

PHP