PHP 字符串截取和随机字符串函数封装

 /**
 *把字符串分割为数组(一维数组)
 *@$str string  分割的字符串
 *@$charset string 字符串编码
 */
function str_cut($str,$charset='utf-8'){
    $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);
    return $match[0];
}

//返回随机字符串
function randomString($l=5,$mode="n",$config=[],$charset="utf-8"){
    $C=[
        "n"		=>	"0123456789"
        ,"s"		=>	"abcdefghijklmnopqrstuvwxyz"
        ,"S"		=>	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        ,"ns"		=>	"0123456789abcdefghijklmnopqrstuvwxyz"
        ,"nS"		=>	"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        ,"sS"		=>	"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        ,"nsS"		=>	"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        ,"all"		=>	"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-_^+*=|,.~!@#"
    ];
    if (is_array($config)) {
        foreach ($config as $key => $value) {
            $C[$key]=str_cut($value, $charset);
        }
    }
    $mode= empty($C[$mode]) ? "n"	:	$mode ;
    $str=""; if(is_array($C[$mode]) && count($C[$mode])>0 ){
        for($i=0,$len=count($C[$mode]);$i<$l;$i++){
            $str.=$C[$mode][mt_rand(0,$len-1)];
        }
    }
    else{
        for($i=0,$len=strlen($C[$mode]);$i<$l;$i++){
            $str.=$C[$mode][mt_rand(0,$len-1)];
        }
    }
    return $str;
}

/**
 * 字符串截取
 * @$str string 要截取的字符串
 * @$start number 要截取的开始位置，从0开始
 * @$length nunber 截取的长度
 * @$charset string 字符串编码
 */
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);
        if (false === $slice) {
            $slice = '';
        }
    } 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));
    }
    //字数不满不添加...
    $count = mb_strlen($str, 'utf-8');
    if ($count > $length) {
        return $suffix ? $slice . '......' : $slice;
    } else {
        return $slice;
    }
}