rand

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

rand — Generate 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

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User Contributed Notes 1 note

down

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).

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