什么是在PHP中生成16长度随机数的最佳方法？ [关闭]

Question

I want to generate a random number code in PHP without repeat and with 16 lengths. What's the best way to do this? I use this code :

$possible = '0123456789';
$code = '';
$i = 0;
while ($i < 14) {
    $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
    $i++;
}
echo($code);

But that is generating 1 random number. I want 30000 random numbers. What shall I do ?

i use this code too but that is not generate 16 length :

<?php

    $con=mysqli_connect("localhost","root","","test1");
    // Check connection
    if (mysqli_connect_errno()) {
        echo "Failed to connect to MySQL: " . mysql_connect_error();
    }
    for ($s=0;$s<10;$s++) {
        $possible = '0123456789';
        $code = '';
        $i = 0;
    while ($i < 16) {
        $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
        $i++;
    }
    echo($code);
    echo nl2br("$code <br/>");

    mysqli_query($con,"INSERT INTO test (ID, Code, Type, Used)
    VALUES ('', '".$code."','1', '0')");
    }
    for ($s=0;$s<10;$s++) {
        $possible = '0123456789';
        $code = '';
        $i = 0;
    while ($i < 16) {
        $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
        $i++;
    }
    echo($code);
    echo nl2br("$code <br/>");

    mysqli_query($con,"INSERT INTO test (ID, Code, Type, Used)
    VALUES ('', '".$code."','2', '0')");
    }
    for ($s=0;$s<10;$s++) {
        $possible = '0123456789';
        $code = '';
        $i = 0;
    while ($i < 16) {
        $code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);
        $i++;
    }
    echo($code);
    echo nl2br("$code <br/>");

    mysqli_query($con,"INSERT INTO test (ID, Code, Type, Used)
    VALUES ('', '".$code."','3', '0')");
    }
    mysqli_close($con);
?>

Answer 1

Snippet for no repeating digits:

$len=14;
$last=-1;
for ($i=0;$i<$len;$i++)
{
    do
    {
        $next_digit=mt_rand(0,9);
    }
    while ($next_digit == $last);
    $last=$next_digit;
    $code.=$next_digit;
}

---

Snippet for no duplicates within 30000 (but repeating digits are allowed):

$codes=array();
while (count($codes) < 30000)
{
    $code=rand(pow(10,13),pow(10,14)-1);
    $codes["$code"]=1;
}

The codes are stored as the keys of the array (just to save some memory).

There might be better solutions for this problem (especially with more efficient ones) - but this one is really short ;-) - due to the integration of Kolink's solution.

Hope it helps a bit.

*Jost