distribution

dist.php

<?php
function randomInt(int $min, int $max) :int
	{

    if (!is_int($min)) {
        throw new \Exception('First parameter ($min) must be an integer');
    }

    if (!is_int($max)) {
        throw new \Exception('Second parameter ($max) must be an integer');
    }

    if ($min > $max) {
        throw new \Exception('First parameter ($min) must be no greater than second parameter ($max)');
    }

    if ($min === $max) {
        return $min;
    }

    // $range is a PHP float if the expression exceeds PHP_INT_MAX.
    $range = $max - $min + 1;

    if (is_float($range)) {
        $mask = null;
    } else {
        // Make a bit mask of (the next highest power of 2 >= $range) minus one.
        $mask = 1;
        $shift = $range;
        while ($shift > 1) {
            $shift >>= 1;
            $mask = ($mask << 1) | 1;
        }
    }

    $tries = 0;
    do {
        $bytes = random_bytes(PHP_INT_SIZE);

        // Convert byte string to a signed int by shifting each byte in.
        $value = 0;
        for ($pos = 0; $pos < PHP_INT_SIZE; $pos += 1) {
            $value = ($value << 8) | ord($bytes[$pos]);
        }

        if ($mask === null) {
            // Use all bits in $bytes and check $value against $min and $max instead of $range.
            if ($value >= $min && $value <= $max) {
                return $value;
            }
        } else {
            // Use only enough bits from $bytes to cover the $range.
            $value &= $mask;
            if ($value < $range) {
                return $value + $min;
            }
        }

        $tries += 1;
    } while ($tries < 123);

    // Worst case: this is as likely as 123 heads in as many coin tosses.
    throw new \Exception('Unable to generate random int after 123 tries');
	}

/*source: https://stackoverflow.com/questions/40644040/how-to-generate-a-random-number-from-a-uniform-distribution-in-php
just simulating dice rolls here
*/
function testRand($randFunction, $groupsNumber = 6, $rollsNumber = 4000000)
{
    $frequencies = array_fill(0, $groupsNumber, 0);
    foreach (range(1, $rollsNumber) as $ignored) {
        $frequencies[$randFunction(0, $groupsNumber - 1)]++;
    }

    echo PHP_EOL, "------- results for `$randFunction` -------", PHP_EOL;
    $cum = 0;
    foreach ($frequencies as $index => $frequency) {
        $percent = $frequency * 100 / $rollsNumber;
        $cum += $percent;
        echo sprintf("%d\t|\t%4d\t%6.2f\t%6.2f", 
                     $index, $frequency, $percent, $cum), 
             PHP_EOL;
    }
}
testRand('randomInt');