random_int

(PHP 7, PHP 8)

random_intGet a cryptographically secure, uniformly selected integer

Descrizione

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

Generates a uniformly selected integer between the given minimum and maximum.

The randomness generated by this function is suitable for all applications, including the generation of long-term secrets, such as encryption keys.

The sources of randomness in the order of priority are as follows:

  • Linux: » getrandom(), /dev/urandom

  • FreeBSD >= 12 (PHP >= 7.3): » getrandom(), /dev/urandom

  • Windows (PHP >= 7.2): » CNG-API

    Windows: » CryptGenRandom

  • macOS (PHP >= 8.2; >= 8.1.9; >= 8.0.22 if CCRandomGenerateBytes is available at compile time): CCRandomGenerateBytes()

    macOS (PHP >= 8.1; >= 8.0.2): arc4random_buf(), /dev/urandom

  • NetBSD >= 7 (PHP >= 7.1; >= 7.0.1): arc4random_buf(), /dev/urandom

  • OpenBSD >= 5.5 (PHP >= 7.1; >= 7.0.1): arc4random_buf(), /dev/urandom

  • DragonflyBSD (PHP >= 8.1): » getrandom(), /dev/urandom

  • Solaris (PHP >= 8.1): » getrandom(), /dev/urandom

  • Any combination of operating system and PHP version not previously mentioned: /dev/urandom
  • If none of the sources are available or they all fail to generate randomness, then a Random\RandomException will be thrown.

Nota: Although this function was added to PHP in PHP 7.0, a » userland implementation is available for PHP 5.2 to 5.6, inclusive.

Elenco dei parametri

min

The lowest value to be returned.

max

The highest value to be returned.

Valori restituiti

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

Errori/Eccezioni

Log delle modifiche

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

Esempi

Example #1 random_int() example

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

Il precedente esempio visualizzerĂ  qualcosa simile a:

int(248)
int(-898)

Vedere anche:

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User Contributed Notes 4 notes

up
10
s rotondo90 at gmail com
8 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
3
bens at effortlessis dot com
4 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.
up
0
Hayley Watson
1 year ago
A small function for generating version 4 GUIDs.

<?php
function v4uuid()
{
   
$a = str_pad(dechex(random_int(0x0000_0000, 0xffff_ffff)), '0', STR_PAD_LEFT);
   
$b = str_pad(dechex(random_int(0x0000, 0xffff)), '0', STR_PAD_LEFT);
   
$c = dechex(random_int(0x4000, 0x4fff));
   
$d = dechex(random_int(0x8000, 0xbfff));
   
$e = str_pad(dechex(random_int(0x0000_0000_0000, 0xffff_ffff_ffff)), '0', STR_PAD_LEFT);
    return
"$a-$b-$c-$d-$e";
}
?>
up
0
ccb_bc at hotmail dot com
5 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());
?>
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