Web студия "GrandView"

Описание

int rand ( [int min, int max] )

При вызове без параметров min и max, возвращает псевдослучайное целое в диапазоне от 0 до RAND_MAX. Например, если вам нужно случайное число между 5 и 15 (включительно), вызовите rand (5, 15).

Пример 1. Пример

<?php echo rand() . "\n"; echo rand() . "\n"; echo rand(5, 15); ?>
Пример выше выведет что-то наподобие этого:
7771 22264 11

Замечание: На некоторых платформах (таких как Windows) RAND_MAX всего лишь 32768. Чтобы расширить диапазон, используйте параметры min и max, или обратитесь к функции mt_rand().

Замечание: Начиная с PHP 4.2.0, больше нет необходимости инициализировать генератор случайных чисел функциями srand() или mt_srand(), поскольку теперь это происходит автоматически.

Замечание: В версиях до 3.0.7 max определяло диапазон генерирования. Например, чтобы получить число от 5 до 15, нужно было вызвать rand (5, 11).

См. также: srand(), getrandmax() и mt_rand().

add a note User Contributed Notes
rand

Ishtar
10-Sep-2007 06:18


A small comment on phpdev-dunnbypauls conclusion that rand() only generates numbers that are a multiply of 3. 

<?php

$n = rand(0,100000); // with MAX_RAND=32768

?>

Since, 100000/32768=3.05 you get multiples of 3. The random integer will be multiplied by 3.05 to fit between 0 and 100000. rand() works fine, if you don't ask for bigger numbers then RAND_MAX.

jfkallen at hotmail dot com
17-Aug-2007 07:21


In regards to mno2go's note below on randomly generated strings, I am not sure what's inefficient about this.  I like it and am using it in several modules (so thanks).  I made a few tweaks though.  There is a fence-post error in the code (a string's range is 0 to n-1).  There is also excessive calls to strlen.



<?php

    function generateCode($length=6) {

        $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPRQSTUVWXYZ0123456789";

        $code = "";

        $clen = strlen($chars) - 1;  //a variable with the fixed length of chars correct for the fence post issue

        while (strlen($code) < $length) {

            $code .= $chars[mt_rand(0,$clen)];  //mt_rand's range is inclusive - this is why we need 0 to n-1

        }

        return $code;

    }

?>

alishahnovin at hotmail dot com
13-Aug-2007 10:39


Quick function that returns an array of unequal random numbers. Works well if you need to assign random values, but want them to all be unique.



<?php

function randiff($min, $max, $num) {

    if ($min<$max && $max-$min+1 >= $num && $num>0) {

        $random_nums = array();

        $i=0;

        while($i<$num) {

            $rand_num = rand($min, $max);

            if (!in_array($rand_num, $random_nums)) {

                $random_nums[] = $rand_num;

                $i++;

            }

        }

        return $random_nums;

    } else {

        return false;

    }

}

?>



So rather than:



<?php

$var1 = rand(0,10);

$var2 = rand(0,10);

?>



Which could potentially give you two of the same values, you can use:



<?php

$nums = randiff(0,10,2);

$var1 = $nums[0];

$var2 = $nums[1];

?>

mno2go at gmail dot com
03-Aug-2007 02:30


Perhaps not the most efficient way, but one that is quite simple and provides for easy control over characters used in the generated strings/passwords:



<?php

    function generateCode($length=6) {

        $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPRQSTUVWXYZ0123456789";

        $code = "";

        while (strlen($code) < $length) {

            $code .= $chars[mt_rand(0,strlen($chars))];

        }

        return $code;

    }

?>

rok dot kralj at gmail dot com
16-Jun-2007 12:43


rand function returns just a whole numbers. If you want a random float, then here's an elegant way:



<?php

function random_float ($min,$max) {

   return ($min+lcg_value()*(abs($max-$min)));

}

?>

bozo_z_clown at yahoo dot com
23-May-2007 05:36


Note that the automatic seeding seems to be done with the current number of seconds which means you can get the same results for several runs on a fast server.  Either call srand() yourself with a more frequently changing seed or use mt_rand() which doesn't appear to suffer from the problem.

blackened at live dot com
29-Apr-2007 08:24


DKDiveDude forgot one thing in his function.

I tested it, and I found out the random output could even be smaller then $intMin.

This was because he forgot to multiply $intMin with $intPowerTen.

Below DKDiveDude's function with the edit



<?php

// Floating point random number function

// April 2007, Ren