PHP通用字符串截取函数

/**
 * 字符串截取通用函数
 * @param  string  $str     要截取的字符串
 * @param  integer $start   截取开始位置
 * @param  integer  $length  截取长度
 * @param  string  $charset 字符串编码格式
 * @param  boolean $suffix  是否显示省略符号
 * @return string           截取后的字符串
 */
function msubstr($str, $start = 0, $length, $charset = "utf-8", $suffix = false) { 
    if (function_exists("mb_substr")) { 
        if ($suffix) 
            return mb_substr($str, $start, $length, $charset) . "..."; 
        else 
            return mb_substr($str, $start, $length, $charset); 
    } elseif (function_exists("iconv_substr")) { 
        if ($suffix) 
            return iconv_substr($str, $start, $length, $charset) . "..."; 
        else 
            return iconv_substr($str, $start, $length, $charset); 
    } 
    $re["utf-8"] = "/[x01-x7f]|[xc2-xdf][x80-xbf]|[xe0-xef][x80-xbf]{2}|[xf0-xff][x80-xbf]{3}/"; 
    $re["gb2312"] = "/[x01-x7f]|[xb0-xf7][xa0-xfe]/"; 
    $re["gbk"] = "/[x01-x7f]|[x81-xfe][x40-xfe]/"; 
    $re["big5"] = "/[x01-x7f]|[x81-xfe]([x40-x7e]|xa1-xfe])/"; 
    preg_match_all($re[$charset], $str, $match); 
    $slice = join("", array_slice($match[0], $start, $length)); 
    if ($suffix) 
        return $slice . "…";  
    return $slice; 
}
echo msubstr("测试PHP字符串截取", 2, 5, "utf-8", true);
//结果：PHP字符...