/**
 * @param $length
 * @return string
 * 生成随机字符串
 */
function getNonceStr($length = 4)
{
    $chars = "abcdefghijkmnpqrstuvwxyz23456789";
    $str ="";
    for ( $i = 0; $i < $length; $i++ )  {
        $str .= substr($chars, mt_rand(0, strlen($chars)-1), 1);
    }
    return $str;
}
// 生成10位邀请码，用户MD5的前4位和微秒的前6位，把4替换成6寓意好。
function createIntroducerCode($user){
      $d=str_replace('4', '6', substr(md5($user), 0,4).substr(microtime(), 2, 6));
    return $d;
}
 //生成唯一订单号
function build_order_no(){
      return date('Ymd').substr(implode(NULL, array_map('ord', str_split(substr(uniqid(), 7, 13), 1))), 0, 8);
}
//guid
if (!function_exists('guid')) {
    function guid(){
        $uuid = '';
        
            mt_srand((double)microtime()*10000);//optional for php 4.2.0 and up.
            $charid = strtoupper(md5(uniqid(rand(), true)));
            $hyphen = chr(45);// "-"
            //$uuid = //chr(123)// "{"
            $uuid .= substr($charid, 0, 8).$hyphen
            .substr($charid, 8, 4).$hyphen
            .substr($charid,12, 4).$hyphen
            .substr($charid,16, 4).$hyphen
            .substr($charid,20,12);
            //.chr(125);// "}"
            return $uuid;
        
    }
}
function createUUID(){
       return sprintf( '%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
            // 32 bits for "time_low"
            mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ),

            // 16 bits for "time_mid"
            mt_rand( 0, 0xffff ),

            // 16 bits for "time_hi_and_version",
            // four most significant bits holds version number 4
            mt_rand( 0, 0x0fff ) | 0x4000,

            // 16 bits, 8 bits for "clk_seq_hi_res",
            // 8 bits for "clk_seq_low",
            // two most significant bits holds zero and one for variant DCE1.1
            mt_rand( 0, 0x3fff ) | 0x8000,

            // 48 bits for "node"
            mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff ), mt_rand( 0, 0xffff )
        );
}