Generate a random value via the Mersenne Twister Random Number Generator

# mt_rand

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

mt_rand — 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)`.

Caution

This function does not generate cryptographically secure values, and must not be used for cryptographic purposes, or purposes that require returned values to be unguessable.

If cryptographically secure randomness is required, the Random\Randomizer may be used with the Random\Engine\Secure engine. For simple use cases, the random_int() and random_bytes() functions provide a convenient and secure API that is backed by the operating system’s CSPRNG.

Caution

This function uses the global Mt19937 (“Mersenne Twister”) instance as the source of randomness and thus shares its state with all other functions using the global Mt19937. Using any of these functions advances the sequence for all the other functions, regardless of scope.

Generating repeatable sequences by seeding mt_srand() or srand() with a known value will also yield repeatable output from this function.

Prefer using Random\Randomizer methods in all newly written code.

### 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

Example #1 mt_rand() example

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

The above example will output something similar to:

    1604716014
    1478613278
    6

### Notes

Warning

`min` `max` 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.

### See Also

- mt_srand() - Seeds the Mersenne Twister Random Number Generator
- mt_getrandmax() - Show largest possible random value
- random_int() - Get a cryptographically secure, uniformly selected integer
- random_bytes() - Get cryptographically secure random bytes

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