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    mt_rand

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

    mt_rand — Generate a random value via the Mersenne Twister Random Number Generator

    Descrição

    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).

    Cuidado

    Esta função não gera valores criptograficamente seguros e não deve ser usada para propósitos criptográficos ou fins que exijam que os valores retornados sejam impossíveis de adivinhar.

    Se aleatoriedade criptograficamente segura for necessária, a classe Random\Randomizer pode ser usada com o mecanismo Random\Engine\Secure. Para casos de uso simples, as funções random_int() e random_bytes() fornecem uma API conveniente e segura que é garantida pelo CSPRNG do sistema operacional.

    Parâmetros

    min

    Optional lowest value to be returned (default: 0)

    max

    Optional highest value to be returned (default: mt_getrandmax())

    Valor Retornado

    A random integer value between min (or 0) and max (or mt_getrandmax(), inclusive), or false if max is less than min.

    Registro de Alterações

    Versão Descrição
    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.

    Exemplos

    Exemplo #1 mt_rand() example

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

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

    O exemplo acima produzirá algo semelhante a:

    1604716014
1478613278
6

    Notas

    Aviso

    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.

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    User Contributed Notes 3 notes

    up
    13
    Pawe Krawczyk
    11 years ago
    To reiterate the message about *not* using mt_rand() for anything security related, here's a new tool that has been just posted that recovers the seed value given a single mt_rand() output:

    http://www.openwall.com/php_mt_seed/README
    up
    7
    greald at ghvernuft dot nl
    1 year ago
    To see some systematic deviations from a universal distribution run:

    <?php
    $alfabet     = str_split('ADHKLMNPSTUWX');
    $countalfabet = count($alfabet)-1;
    $code = array_fill_keys($alfabet, 0);
    for (    $L=0; $L<80*$countalfabet; $L++)
    {
          $lettr = floor(mt_rand ( 0, $countalfabet ));
          $code[$alfabet[$lettr]]++;
    }

    foreach(    $code as $L => $Freq)
    {
      for(    $F=0; $F<$Freq; $F++)
      {
        echo     $L;
      }
      echo     "\n<br/>";
    }
    ?>
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