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rand

(PHP 4, PHP 5, PHP 7, PHP 8)

randGenerate a random integer

Descripción

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

If called without the optional min, max arguments rand() returns a pseudo-random integer between 0 and getrandmax(). If you want a random number between 5 and 15 (inclusive), for example, use rand(5, 15).

Precaución

Esta función no genera valores criptográficos fiables por lo que no debería empelarse para propósitos criptográficos. Si fuera necesario un valor criptográfico seguro, considérese utilizar random_int(), random_bytes(), o openssl_random_pseudo_bytes() en su lugar.

Nota: On some platforms (such as Windows), getrandmax() is only 32767. If you require a range larger than 32767, specifying min and max will allow you to create a range larger than this, or consider using mt_rand() instead.

Nota: As of PHP 7.1.0, rand() uses the same random number generator as mt_rand(). To preserve backwards compatibility rand() allows max to be smaller than min as opposed to returning false as mt_rand().

Parámetros

min

The lowest value to return (default: 0)

max

The highest value to return (default: getrandmax())

Valores devueltos

A pseudo random value between min (or 0) and max (or getrandmax(), inclusive).

Historial de cambios

Versión Descripción
7.2.0 rand() has received a bug fix for a modulo bias bug. This means that sequences generated with a specific seed may differ from PHP 7.1 on 64-bit machines.
7.1.0 rand() has been made an alias of mt_rand().

Ejemplos

Ejemplo #1 rand() example

<?php
echo rand(), "\n";
echo
rand(), "\n";

echo
rand(5, 15), "\n";
?>

El resultado del ejemplo sería algo similar a:

7771
22264
11

Notas

Advertencia

min max range must be within the range getrandmax(). i.e. (max - min) <= getrandmax() Otherwise, rand() may return poor-quality random numbers.

Ver también

  • srand() - Seed the random number generator
  • getrandmax() - Show largest possible random value
  • mt_rand() - Generate a random value via the Mersenne Twister Random Number Generator
  • random_int() - Get a cryptographically secure, uniformly selected integer
  • random_bytes() - Get cryptographically secure random bytes

add a note

User Contributed Notes 4 notes

up
3
play dot it at play-it dot net
1 year ago
Here is a simple base64 random string function

<?php
function random_string($length) {
$str = random_bytes($length);
$str = base64_encode($str);
$str = str_replace(["+", "/", "="], "", $str);
$str = substr($str, 0, $length);
return
$str;
}

/*
Example outputs for random_string(32)

OP0vOJEsSvr6wbgN4jIwqMMstlpMSUsl
2IHaIxD2W4VTKZuzioudbpQCALdl6Ym6
QY0eZ3QYy3OKKN6ttzbDwAwsAfkXfQ2f
jznjlPCUDbYzOTJysPP414BbdVNu4jmT
GlktgJ8JUhdH5MfQ1PHl0wnqXQlKggQs
Pb9WALM3KcGCCPBKXsPgNfy3M0Xj4aEu
AED6OTVl8aBbspdxoXvA1sT4ein8lruH
9cSbz4FhoI4qSsPZFMh0u1rWDDEgQxI2
iSBlT4K7Ad516qPXgPReSj2tii7TAK5b
DuX8HByMb2e8IdM4j49Td2JTI9Ki7o1C
*/
?>
up
3
relsqui at armory dot com
19 years ago
Don't forget, it's faster to use bitwise operations when you need a random number that's less than some power of two. For example,

<?php
rand
()&1;
// instead of
rand(0,1);
// for generating 0 or 1,

rand()&3;
// instead of
rand(0,3);
// for generating 0, 1, 2, or 3,

rand()&7;
// instead of
rand(0,7)
// for generating 0, 1, 2, 3, 4, 5, 6, or 7,
?>

and so on. All you're doing there is generating a default random number (so PHP doesn't have to parse any arguments) and chopping off the piece that's useful to you (using a bitwise operation which is faster than even basic math).
up
-5
Anonymous
3 years ago
Note that the algorithm change in version 7.1.0 broke the repeatability of a random sequence initialized with a given value. For example if you have a program like:

<?php
srand
($argv[1]);
for (
$i = 0; $i < 10; $i++) {
echo
rand().PHP_EOL;
}
?>

It will will no longer produce the same results after version 7.1.0. This can be very important for some kinds of simulations. Hopefully you were using mt_rand() or something better all along, otherwise you will have some digging to do if you want your program to be able to repeat simulations from the pre-7.1.0 days... You will need to look in the PHP source archives to discover the algorithm they used to use and replicate it in your program.
up
-11
Anonymous
14 years ago
Generate a random 5 character A-Z0-9 string

<?php
for ($i=0; $i<6; $i++) {
$d=rand(1,30)%2;
echo
$d ? chr(rand(65,90)) : chr(rand(48,57));
}
?>

# php -r 'for ($i=0; $i<6; $i++) { $d=rand(1,30)%2; echo $d ? chr(rand(65,90)) : chr(rand(48,57)); } echo "\n";'
14BW1A
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