php 字符串截取 php如何截取字符串

/**

* 字符串截取，支持中文和其他编码

* @param string $str 需要转换的字符串

* @param string $start 开始位置

* @param string $length 截取长度

* @param string $charset 编码格式

* @param string $suffix 截断显示字符

* @return string

*/

function msubstr($str, $start=0, $length, $charset="utf-8", $suffix=true) {

if(function_exists("mb_substr"))

$slice = mb_substr($str, $start, $length, $charset);

elseif(function_exists('iconv_substr')) {

$slice = iconv_substr($str,$start,$length,$charset);

}else{

$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));

}

return ($suffix && (mb_strlen($str,$charset) > $length)) ? $slice.'...' : $slice;

}