PHP CDKEY Coupon Number Generation Source

<?php

//Returns a random number with a specified number of digits, up to 10. If 4, a random number between 1000 and 9999.

function get_rand_number($len=4) {

    $len = abs((int)$len);

    if ($len < 1) $len = 1;

    else if ($len > 10) $len = 10;

    return rand(pow(10, $len - 1), (pow(10, $len) - 1));

}

//Converts the passed three-digit number to hexadecimal and returns it. Used only through preg_match_callback.

function get_simple_36($m){

    $str = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';

    $div = floor($m[0] / 36);

    $rest = $m[0] % 36;

    return $str[$div] . $str[$rest];

}

//Returns an array of all the prime numbers that exist in the specified number of digits. max len = 5

function get_simple_prime_number($len=5){

    $len = abs((int)$len);

    if ($len < 1) $len = 1;

    else if ($len > 5) $len = 5;

    $prime_1 = Array(1, 2, 3, 5, 7);

    if ($len == 1) return $prime_1;

    $start = pow(10, ($len - 1)) + 1;//101

    $end = pow(10, $len) - 1;//999

    $prime = $prime_1;

    unset($prime[0]);//Remove 1

    unset($prime[1]);//Remove 2

    $array = Array();

    for($i = 11; $i <= $end; $i+=2){//There are no even prime numbers greater than 10.

        $max = floor(sqrt($i));

        foreach($prime as $j) {

            if ($j > $max) break;

            if ($i % $j == 0) continue 2;

        }

        $prime[] = $i;

        if ($i >= $start) $array[] = $i;

    }

    return $array;

}

//Returns a serial with a specified number of digits. If you don't want to include -, $cut must be greater than or equal to $len. max len = 36

 function get_serial($len=16, $cut=4, $hipen='-'){

    $len = abs((int)$len);

    if ($len < 1) $len = 16;

    else if ($len > 36) $len = 36;

    $cut = abs((int)$cut);

    if ($cut < 1) $cut = 4;

    else if ($cut > $len) $cut = $len;

    list($usec, $sec) = explode(' ', microtime());

    $base_number = (string)$sec . str_replace('0.', '', (string)$usec);

    $base_number .= (string)get_rand_number(10) . (string)get_rand_number(8);//36 digit unique numeric string

    $prime = get_simple_prime_number(5);//5 digit decimal array

    shuffle($prime);

    $prime = $prime[0];//random 5 digit prime number

    $serial = bcmul(substr($base_number, 0, $len), $prime);

    $serial_length = strlen($serial);

    $sub = $len - $serial_length;

    if ($sub > 0) $serial .= (string)get_rand_number($sub);

    else if ($sub < 0) $serial = substr($serial, 0, $len);

    return preg_replace("`(.{" . $cut . "})`", "$1" . $hipen, $serial, floor(($len-1) / $cut));

}

//Returns a serial with a number and an English letter with a specified number of digits. If you don't want to include -, $cut must be greater than or equal to $len. max len = 24

function get_serial_mix($len=16, $cut=4, $hipen='-'){

    $len = abs((int)$len);

    if ($len < 1) $len = 16;

    else if ($len > 24) $len = 24;

    $cut = abs((int)$cut);

    if ($cut < 1) $cut = 4;

    else if ($cut > $len) $cut = $len;

    $len2 = (int)($len * 3 / 2);

    if ($len2 % 2 == 1) $len2 += 1;

    $serial = get_serial($len2, $len2, $hipen);

    $serial = substr(preg_replace_callback("`.{3}`", "get_simple_36", $serial), 0, $len);

    return preg_replace("`(.{" . $cut . "})`", "$1" . $hipen, $serial, floor(($len-1) / $cut));

}

echo get_serial_mix(36, 4, '-');

?>