random_int

(PHP 7, PHP 8)

random_intGet a cryptographically secure, uniformly selected integer

Descrição

random_int(int $min, int $max): int

Generates cryptographic random integers that are suitable for use where unbiased results are critical, such as when shuffling a deck of cards for a poker game.

As fontes de aleatoriedade dessa função são:

Nota: Embora essa função tenha sido adicionado no PHP 7.0, existe » implementação userland disponível para PHP 5.2 ao 5.6.

Parâmetros

min

The lowest value to be returned.

max

The highest value to be returned.

Valor Retornado

A cryptographically secure, uniformly selected integer from the closed interval [min, max]. Both min and max are possible return values.

Erros

  • Se uma fonte de aleatoriedade não for encontrada uma Random\RandomException será lançada.
  • No caso de parâmetros inválidos um TypeError será lançado.
  • If max is less than min, an ValueError will be thrown.

Changelog

Versão Descrição
8.2.0 In case of a CSPRNG failure, this function will now throw a Random\RandomException. Previously a plain Exception was thrown.

Exemplos

Exemplo #1 random_int() example

<?php
var_dump
(random_int(100, 999));
var_dump(random_int(-1000, 0));
?>

O exemplo acima produzirá algo semelhante a:

int(248)
int(-898)

Veja Também

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User Contributed Notes 3 notes

up
14
s rotondo90 at gmail com
6 years ago
Here is a simple backporting function, it works for PHP >= 5.1

<?php
if (!function_exists('random_int')) {
    function
random_int($min, $max) {
        if (!
function_exists('mcrypt_create_iv')) {
           
trigger_error(
               
'mcrypt must be loaded for random_int to work',
               
E_USER_WARNING
           
);
            return
null;
        }
       
        if (!
is_int($min) || !is_int($max)) {
           
trigger_error('$min and $max must be integer values', E_USER_NOTICE);
           
$min = (int)$min;
           
$max = (int)$max;
        }
       
        if (
$min > $max) {
           
trigger_error('$max can\'t be lesser than $min', E_USER_WARNING);
            return
null;
        }
       
       
$range = $counter = $max - $min;
       
$bits = 1;
       
        while (
$counter >>= 1) {
            ++
$bits;
        }
       
       
$bytes = (int)max(ceil($bits/8), 1);
       
$bitmask = pow(2, $bits) - 1;

        if (
$bitmask >= PHP_INT_MAX) {
           
$bitmask = PHP_INT_MAX;
        }

        do {
           
$result = hexdec(
               
bin2hex(
                   
mcrypt_create_iv($bytes, MCRYPT_DEV_URANDOM)
                )
            ) &
$bitmask;
        } while (
$result > $range);

        return
$result + $min;
    }
}
?>

Randomness test

<?php
$max
= 100; // number of random values
$test = 1000000;

$array = array_fill(0, $max, 0);

for (
$i = 0; $i < $test; ++$i) {
    ++
$array[random_int(0, $max-1)];
}

function
arrayFormatResult(&$item) {
    global
$test, $max; // try to avoid this nowdays ;)
   
   
$perc = ($item/($test/$max))-1;
   
$item .= ' '. number_format($perc, 4, '.', '') .'%';
}

array_walk($array, 'arrayFormatResult');

print_r($array);
?>
up
7
ccb_bc at hotmail dot com
3 years ago
<?php
   
// PHP >= 7
   
function str_rand(int $length = 16){
       
$x = '';
        for(
$i = 1; $i <= $length; $i++){
           
$x .= dechex(random_int(0,255));
        }
        return
substr($x, 0, $length);
    }
   
var_dump(str_rand());
?>
up
3
bens at effortlessis dot com
2 years ago
On my system (5th gen i7) random_int() takes about 14x longer to do the same number of calculations than rand().

for ($i=0; $i<10000000; $i++)
        $x = rand(1, PHP_INT_MAX);

Takes 0.86 seconds for rand(), 12.29 seconds for random_int(). So use random_int() somewhat sparingly.

If it's not really important to be truly random, use rand() instead, especially in a tight loop.
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