mt_getrandmax - PHP code example

Using the PHP Function mt_getrandmax

When developing a web application, there are times when it is useful to have random number functions. This can be done for a variety of reasons like giving visitors different greetings, adding a sense of randomness to games, or securing data through hashing. Whatever the purpose, randomisation is easy in PHP thanks to a few simple functions.

mt_getrandmax is one such function that allows us to create random integers in a range. mt stands for Mersenne Twister, which is an algorithm for generating random numbers that is much faster than older ones.

The function takes two parameters: minv and maxv, which are the lowest and highest value to generate a range of numbers from. The function will then return a randomly generated integer value in this range. The function will not return a value that is equal to maxv, so it is important to always include the maxv parameter.

Using the mt_getrandmax function is a better choice than the rand() function because it has a lot more randomness in it than rand() does. The reason for this is because it uses a Mersenne Twister algorithm which is faster than other algorithms such as rand(), and it will generate far more random numbers that are within a range of values you choose.

In PHP 8.2, this function and other functions related to random number generation have been moved to the random extension, which organizes and consolidates existing PHP functionality into a single library. The new random extension is bundled with PHP so there should be no practical difference for users of existing applications.

mt_getrandmax example

$min = is_numeric($settings['min']) ? $settings['min'] : -pow(10, ($precision - $scale)) + 1;

    // Get the number of decimal digits for the $max     $decimal_digits = self::getDecimalDigits($max);
    // Do the same for the min and keep the higher number of decimal digits.     $decimal_digits = max(self::getDecimalDigits($min), $decimal_digits);
    // If $min = 1.234 and $max = 1.33 then $decimal_digits = 3     $scale = rand($decimal_digits, $scale);

    // @see "Example #1 Calculate a random floating-point number" in     // http://php.net/manual/function.mt-getrandmax.php     $random_decimal = $min + mt_rand() / mt_getrandmax() * ($max - $min);
    $values['value'] = self::truncateDecimal($random_decimal, $scale);
    return $values;
  }

  /** * Helper method to get the number of decimal digits out of a decimal number. * * @param int $decimal * The number to calculate the number of decimals digits from. * * @return int * The number of decimal digits. */

/** * {@inheritdoc} */
  public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
    $settings = $field_definition->getSettings();
    $precision = rand(10, 32);
    $scale = rand(0, 2);
    $max = is_numeric($settings['max']) ? $settings['max'] : pow(10, ($precision - $scale)) - 1;
    $min = is_numeric($settings['min']) ? $settings['min'] : -pow(10, ($precision - $scale)) + 1;
    // @see "Example #1 Calculate a random floating-point number" in     // http://php.net/manual/function.mt-getrandmax.php     $random_decimal = $min + mt_rand() / mt_getrandmax() * ($max - $min);
    $values['value'] = self::truncateDecimal($random_decimal, $scale);
    return $values;
  }

}

    public function testPayloadPercentageWithoutAdvancedPricesWithCurrencyFactor(): void
    {
        $currencyFactor = random_int(0, mt_getrandmax()) / mt_getrandmax();
        $maxValue = 23.0;
        $discount = new PromotionDiscountEntity();
        $discount->setId('P123');
        $discount->setType(PromotionDiscountEntity::TYPE_PERCENTAGE);
        $discount->setValue(50);
        $discount->setMaxValue($maxValue);
        $discount->setScope(PromotionDiscountEntity::SCOPE_CART);

        $builder = new PromotionItemBuilder();

        $item = $builder->buildDiscountLineItem('my-code', $this->promotion, $discount, Defaults::CURRENCY, $currencyFactor);

    return substr($string, 0, $end);
  }

  /** * SQLite compatibility implementation for the RAND() SQL function. */
  public static function sqlFunctionRand($seed = NULL) {
    if (isset($seed)) {
      mt_srand($seed);
    }
    return mt_rand() / mt_getrandmax();
  }

  /** * SQLite compatibility implementation for the REGEXP SQL operator. * * The REGEXP operator is natively known, but not implemented by default. * * @see http://www.sqlite.org/lang_expr.html#regexp */
  public static function sqlFunctionRegexp($pattern, $subject) {
    // preg_quote() cannot be used here, since $pattern may contain reserved

/** * This test verifies that the immutable LineItem Type from * the constructor is correctly used in the LineItem. * * @group promotions * * @throws CartException * @throws UnknownPromotionDiscountTypeException */
    public function testLineItemType(): void
    {
        $currencyFactor = random_int(0, mt_getrandmax()) / mt_getrandmax();

        $builder = new PromotionItemBuilder();

        $discount = new PromotionDiscountEntity();
        $discount->setId('D5');
        $discount->setType(PromotionDiscountEntity::TYPE_PERCENTAGE);
        $discount->setValue(50);
        $discount->setScope(PromotionDiscountEntity::SCOPE_CART);

        $item = $builder->buildDiscountLineItem('', $this->promotion, $discount, 'C1', $currencyFactor);