PHP Manual: Generate a better random value

Description

int mt_rand ( void )

int mt_rand ( int $min , int $max )

Many random number generators of older libcs have dubious or unknown characteristics and are slow. By default, PHP uses the libc random number generator with the rand function. The mt_rand function is a drop-in replacement for this. 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).

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), or FALSE if max is less than min.

Changelog

Version	Description
5.3.4	Issues an `E_WARNING` and returns `FALSE` if `max` < `min`.
4.2.0	The random number generator is seeded automatically.

Examples

Example #1 mt_rand example


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

echo mt_rand(5, 15);
?>

The above example will output something similar to:

1604716014
1478613278
6

Notes

Caution

This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using openssl_random_pseudo_bytes instead.