PhpRiot
Become Zend Certified

Prepare for the ZCE exam using our quizzes (web or iPad/iPhone). More info...


When you're ready get 7.5% off your exam voucher using voucher CJQNOV23 at the Zend Store

mt_rand

(PHP 4, PHP 5)

mt_randGenerate 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.
4.2.0The random number generator is seeded automatically.

Examples

Example #1 mt_rand() example

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

echo 
mt_rand(515);
?>

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.

Caution

The distribution of mt_rand() return values is biased towards even numbers on 64-bit builds of PHP when max is beyond 2^32.

See Also

PHP Manual