(Advanced) PHP generates unique membership card number

We use 0-Z (0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ) to represent values ​​0-35 respectively, such as the letter Z representing 35. In this case, I want to get a 5-digit number. The maximum amount of information is 36 raised to the fifth power, 36^5 = 60466176, that is, the maximum 5-digit number is equivalent to a decimal number: 60466176.

For the sake of demonstration in this article, we assume that a club issues a batch of 10-digit membership card numbers. The membership card number consists of a 3-digit city number + a 5-digit card number code + a 2-digit check code. The city number is represented by the area code. For example, 755 represents Shenzhen. The 5-digit card number is composed of a 36-digit card number. The next two check codes are generated through a certain algorithm. The purpose of the check code is to verify the card number. legality. In this case, the 10-digit card number we generate is equivalent to a maximum of more than 60 million membership card numbers, and it is a unique card number that does not repeat.

We use PHP to convert decimal to hexadecimal.

class Code {
    //密码字典
    private $dic = array(
        0=>'0',    1=>'1', 2=>'2', 3=>'3', 4=>'4', 5=>'5', 6=>'6', 7=>'7', 8=>'8',
        9=>'9', 10=>'A',  11=>'B', 12=>'C', 13=>'D', 14=>'E', 15=>'F',  16=>'G',  17=>'H',
        18=>'I',19=>'J',  20=>'K', 21=>'L',  22=>'M',  23=>'N', 24=>'O', 25=>'P', 26=>'Q',
    27=>'R',28=>'S',  29=>'T',  30=>'U', 31=>'V',  32=>'W',  33=>'X', 34=>'Y', 35=>'Z'
    );


    public function encodeID($int, $format=8) {
        $dics = $this->dic;
        $dnum = 36; //进制数
        $arr = array ();
        $loop = true;
        while ($loop) {
            $arr[] = $dics[bcmod($int, $dnum)];
            $int = bcdiv($int, $dnum, 0);
            if ($int == '0') {
                $loop = false;
            }
        }
        if (count($arr) < $format)
            $arr = array_pad($arr, $format, $dics[0]);

        return implode(&#39;&#39;, array_reverse($arr));
    }

    public function decodeID($ids) {
        $dics = $this->dic;
        $dnum = 36; //进制数
        //键值交换
        $dedic = array_flip($dics);
        //去零
        $id = ltrim($ids, $dics[0]);
        //反转
        $id = strrev($id);
        $v = 0;
        for ($i = 0, $j = strlen($id); $i < $j; $i++) {
            $v = bcadd(bcmul($dedic[$id {
                $i }
            ], bcpow($dnum, $i, 0), 0), $v, 0);
        }
        return $v;
    }

}

We define the Code class, first define the password dictionary, that is, the values ​​corresponding to 0-Z, the parameter $int in the method encodeID($int, $format) represents the number, and $format represents the length of digits, for example encodeID(123456789,5) means converting the number 123456789 into a 5-digit hexadecimal number, and the method decodeID($ids) is used to convert the hexadecimal number into a decimal number.

We can generate the card number like this:

$code = new Code();
$card_no = $code->encodeID(888888,5);

As above, we can get a 5-digit card number, which actually represents the membership number of the card number 888888 (6 eights), and After actual conversion, it is a 5-digit number: 0J1VC.

Next, we add the city number and check code. The city number has been defined, and the check code is obtained through a certain algorithm. In this example, we use a simple algorithm: add the first three The city number and the five-digit card number are md5 encrypted, and then the first two digits of the md5 value are taken as the check code, so that the two-digit check code after the number is obtained.

$card_pre = '755';
$card_vc = substr(md5($card_pre.$card_no),0,2);
$card_vc = strtoupper($card_vc);
echo $card_pre.$card_no.$card_vc;

In actual application, the decimal number can be obtained through the database to ensure that the number is unique, and then the above codes are combined to finally generate a 10-digit non-duplicate membership card number.

Rendering:

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