Generate secure random integers in a uniform distribution

securerandom.php

<?php

function getRandomBits($bits) {
	assert('is_int($bits)');

	/* First load some random bytes. */
	$numBytes = ($bits - 1) / 8 + 1;
	$bytes = openssl_random_pseudo_bytes($numBytes);

	/* Convert it to an integer. */
	$result = 0;
	foreach (str_split($bytes) as $r) {
		$result = $result * 0x100 + ord($r);
	}

	/* Trim it to the required number of bits. */
	$mask = (1 << $bits) - 1;
	$result = $result & $mask;

	return $result;
}

function randRange($min, $max) {
	assert('is_int($min)');
	assert('is_int($max)');
	assert('$min <= $max');

	$range = $max - $min + 1;
	$bits = (int)ceil(log($range) / log(2));

	while (TRUE) {
		$res = getRandomBits($bits);
		if ($res < $range) {
			return $min + $res;
		}
	}
}