function generate_non_overlapping_random_ranges(int $begin, int $end, int $numRanges): array
{
$count = $numRanges * 2;
// ------------------------------------------------------------
// Generate unique random points in [begin, end)
// The random numbers are chaotic and NOT sorted
// ------------------------------------------------------------
$points = [];
while (count($points) < $count) {
$r = rand($begin, $end - 1);
$points[$r] = true; // using keys ensures uniqueness
}
// Convert keys back to a normal array
$points = array_keys($points);
// ------------------------------------------------------------
// Sort the points
// Only AFTER sorting do the ranges become increasing
// and automatically non‑overlapping
// ------------------------------------------------------------
sort($points);
// ------------------------------------------------------------
// Pair adjacent sorted points into (start, end) ranges
// ------------------------------------------------------------
$ranges = [];
for ($i = 0; $i < count($points); $i += 2) {
$ranges[] = [$points[$i], $points[$i + 1]];
}
return $ranges;
}
$start = 1;
$end = 500;
$numRanges = 8;
$ranges = generate_non_overlapping_random_ranges($start, $end, $numRanges);
print_r($ranges);
/*
run:
Array
(
[0] => Array
(
[0] => 38
[1] => 51
)
[1] => Array
(
[0] => 67
[1] => 80
)
[2] => Array
(
[0] => 138
[1] => 179
)
[3] => Array
(
[0] => 193
[1] => 265
)
[4] => Array
(
[0] => 307
[1] => 326
)
[5] => Array
(
[0] => 339
[1] => 355
)
[6] => Array
(
[0] => 418
[1] => 472
)
[7] => Array
(
[0] => 479
[1] => 480
)
)
*/
