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mt_rand

PHP function Edit on GitHub ✎

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

Generate a random value via the Mersenne Twister Random Number Generator

Description

mt_rand(): int

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

Many random number generators of older libcs have dubious or unknown characteristics and are slow. The mt_rand() function is a drop-in replacement for the older rand(). It uses a random number generator with known characteristics using the Mersenne Twister, which will produce random numbers four times faster than what the average libc rand() provides.

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

Cryptographically-insecure Mt19937-global-state

Parameters

min: Optional lowest value to be returned (default: 0)
max: Optional highest value to be returned (default: mt_getrandmax())

Return Values

A random integer value between min (or 0) and max (or mt_getrandmax(), inclusive).

Errors/Exceptions

If max is less than min, a ValueError will be thrown.

Changelog

Version	Description
8.0.0	A `ValueError` will be thrown if `max` is less than `min`; previously an `E_WARNING` was raised, and the function returned false.
7.2.0	`mt_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()`.
7.1.0	`mt_rand()`has been updated to use the fixed, correct, version of the Mersenne Twister algorithm. To fall back to the old behaviour, use `mt_srand()` with `MT_RAND_PHP` as the second parameter.

Examples

mt_rand() example

php

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

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

The above example will output something similar to:

output

1604716014
1478613278
6

Notes

Warning

minmax range must be within the range mt_getrandmax(). i.e. (max - min) <= mt_getrandmax() Otherwise, mt_rand() may return poorer random numbers than it should.