随机 x 位数 - 开卷题库

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You can use rand($min, $max) for that exact purpose.

In order to limit the values to values with x digits you can use the following:

$x = 3; // Amount of digits
$min = pow(10,$x);
$max = pow(10,$x+1)-1);
$value = rand($min, $max);

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Treat your number as a list of digits and just append a random digit each time:

function n_digit_random($digits) {
$temp = "";


for ($i = 0; $i < $digits; $i++) {
$temp .= rand(0, 9);
}


return (int)$temp;
}

Or a purely numerical solution:

function n_digit_random($digits)
return rand(pow(10, $digits - 1) - 1, pow(10, $digits) - 1);
}

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I usually just use RAND() http://php.net/manual/en/function.rand.php

e.g.

rand ( 10000 , 99999 );

for your 5 digit random number

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最佳答案

You can use rand() together with pow() to make this happen:

$digits = 3;
echo rand(pow(10, $digits-1), pow(10, $digits)-1);

This will output a number between 100 and 999. This because 10^2 = 100 and 10^3 = 1000 and then you need to subtract it with one to get it in the desired range.

If 005 also is a valid example you'd use the following code to pad it with leading zeros:

$digits = 3;
echo str_pad(rand(0, pow(10, $digits)-1), $digits, '0', STR_PAD_LEFT);

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do it with a loop:

function randomWithLength($length){


$number = '';
for ($i = 0; $i < $length; $i++){
$number .= rand(0,9);
}


return (int)$number;


}

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rand or mt_rand will do...

usage:

rand(min, max);


mt_rand(min, max);

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function random_numbers($digits) {
$min = pow(10, $digits - 1);
$max = pow(10, $digits) - 1;
return mt_rand($min, $max);
}

Tested here.

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you people really likes to complicate things :)

the real problem is that the OP wants to, probably, add that to the end of some really big number. if not, there is no need I can think of for that to be required. as left zeros in any number is just, well, left zeroes.

so, just append the larger portion of that number as a math sum, not string.

e.g.

$x = "102384129" . complex_3_digit_random_string();

simply becomes

$x = 102384129000 + rand(0, 999);

done.

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this simple script will do

$x = 4;//want number of digits for the random number
$sum = 0;




for($i=0;$i<$x;$i++)
{
$sum = $sum + rand(0,9)*pow(10,$i);


}


echo $sum;

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This is another simple solution to generate random number of N digits:

$number_of_digits = 10;
echo substr(number_format(time() * mt_rand(),0,'',''),0,$number_of_digits);

Check it here: http://codepad.org/pyVvNiof

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the simplest way i can think of is using rand function with str_pad

<?php
echo str_pad(rand(0,999), 5, "0", STR_PAD_LEFT);
?>

In above example , it will generate random number in range 0 to 999.

And having 5 digits.

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function random_number($size = 5)
{
$random_number='';
$count=0;
while ($count < $size )
{
$random_digit = mt_rand(0, 9);
$random_number .= $random_digit;
$count++;
}
return $random_number;
}

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function rand_number_available($already_mem_array,$boundary_min,$boundary_max,$digits_num)
{


$already_mem_array_dim = count($already_mem_array);         // dimension of array, that contain occupied elements


// --- creating Boundaries and possible Errors
if( empty($digits_num) ){
$boundary_dim = $boundary_max - $boundary_min;
if($boundary_dim <= 0){
$error = -1;                                    // Error that might happen. Difference between $boundary_max and $boundary_min must be positive
}else{
$error = -2;                                    // Error that might happen. All numbers between, $boundary_min and $boundary_max , are occupied, by $already_mem_array
}
}else{
if($digits_num < 0){                                // Error. If exist, $digits_num must be, 1,2,3 or higher
$error = -3;
}elseif($digits_num == 1){                          // if 'one-figure' number
$error = -4;                                    // Error that might happen. All 'one-figure' numbers    are occupied, by $already_mem_array
$boundary_min = 0;
$boundary_max = 9;
$boundary_dim = $boundary_max-$boundary_min;
}elseif($digits_num == 2){                          // if 'two-figure' number
$error = -5;                                    // Error that might happen. All 'two-figure' numbers    are occupied, by $already_mem_array
$boundary_min = 10;
$boundary_max = 99;
$boundary_dim = $boundary_max-$boundary_min;
}elseif($digits_num>2){                             // if 'X-figure' number. X>2
$error = -6;                                    // Error that might happen. All 'X-figure' numbers  are occupied, by $already_mem_array. Unlikely to happen
$boundary_min = pow(10, $digits_num-1);         // stepenovanje - graduation
$boundary_max = pow(10, $digits_num)-1;
$boundary_dim = $boundary_max-$boundary_min;
}


}
// -------------------------------------------------------------------




// --- creating response ---------------------------------------------
if( ($already_mem_array_dim <= $boundary_dim)   &&  $boundary_dim>0 ){              // go here only if, there are AVAILABLE numbers to extract, and [difference] $boundary_dim , is positive
do{
$num = rand($boundary_min,$boundary_max);
}while( in_array($num, $already_mem_array) );
$result = $num;
}else{
$result = $error;                                       // Limit that happened
}


return $result;
// -------------------------------------------------------------------


}

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rand(1000, 9999); works more faster than x4 times rand(0,9);

benchmark:

rand(1000, 9999)      : 0.147 sec.
rand(0,9)x4 times     : 0.547 sec.

both functions was running in 100000 iterations to make results more explicit

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Here is a simple solution without any loops or any hassle which will allow you to create random string with characters, numbers or even with special symbols.

$randomNum = substr(str_shuffle("0123456789"), 0, $x);

where $x can be number of digits

substr(str_shuffle("0123456789"), 0, 5);

Results after a couple of executions

You can use the same code to generate random string also, like this

$randomNum=substr(str_shuffle("0123456789abcdefghijklmnopqrstvwxyzABCDEFGHIJKLMNOPQRSTVWXYZ"), 0, $x);

Results with $x = 11

FgHmqpTR3Ox
O9BsNgcPJDb
1v8Aw5b6H7f
haH40dmAxZf
0EpvHL5lTKr

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This function works perfectly with no repeats and desired number of digits.

$digits = '';
function randomDigits($length){
$numbers = range(0,9);
shuffle($numbers);
for($i = 0; $i < $length; $i++){
global $digits;
$digits .= $numbers[$i];
}
return $digits;
}

You can call the function and pass the number of digits for example:

randomDigits(4);

sample results:

4957 8710 6730 6082 2987 2041 6721

Original script got from this gist

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Please not that rand() does not generate a cryptographically secure value according to the docs:

http://php.net/manual/en/function.rand.php

This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using random_int(), random_bytes(), or openssl_random_pseudo_bytes() instead.

Instead it is better to use random_int(), available on PHP 7 (See: http://php.net/manual/en/function.random-int.php).

So to extend @Marcus's answer, you should use:

function generateSecureRandomNumber($digits): int {
return random_int(pow(10, $digits - 1), pow(10, $digits) - 1);
}


function generateSecureRandomNumberWithPadding($digits): string {
$randomNumber = random_int(0, pow(10, $digits) - 1);
return str_pad($randomNumber, $digits, '0', STR_PAD_LEFT);
}

Note that using rand() is fine if you don't need a secure random number.

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Well you can use as simple php function mt_rand(2000,9000) which can generate a 4 digit random number

mt_rand(2000,9000)

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You can generate any x-digit random number with mt_rand() function.

mt_rand() is faster than rand().

Syntax : mt_rand() or mt_rand($min , $max).

Example : <?php echo mt_rand(); ?>