(PHP 7, PHP 8)
random_int — Get a cryptographically secure, uniformly selected integer
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
Note: Although this function was added to PHP in PHP 7.0, a » userland implementation is available for PHP 5.2 to 5.6, inclusive.
minThe lowest value to be returned.
maxThe highest value to be returned.
A cryptographically secure, uniformly selected integer from the closed interval
[min, max]. Both
min and max are
possible return values.
max is less than min, a
ValueError will be thrown.
| Version | Description |
|---|---|
| 8.2.0 | In case of a CSPRNG failure, this function will now throw a Random\RandomException . Previously a plain Exception was thrown. |
Example #1 random_int() example
<?php
var_dump(random_int(100, 999));
var_dump(random_int(-1000, 0));
?>The above example will output something similar to:
int(248) int(-898)
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);
?>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.<?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());
?>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";
}
?>