/*
Select N unique random indices from an existing array in PHP.
Return the indices and print both the index and the corresponding value.
Approach:
- Build an array of indices: 0, 1, 2, ..., size-1.
- Shuffle the indices using shuffle() (Fisher–Yates internally).
- Take the first N shuffled indices — guaranteed unique.
- Return those indices to the caller.
*/
/* Return N unique random indices */
function pick_unique_indices(int $arraySize, int $count): array
{
if ($count > $arraySize) {
throw new InvalidArgumentException(
"Cannot pick more unique indices than array size."
);
}
// Build index list
$indices = range(0, $arraySize - 1);
// Shuffle indices
shuffle($indices);
// Return first N indices
return array_slice($indices, 0, $count);
}
/* Main program */
// Example array
$data = [5, 12, 5, 19, 5, 33, 47, 5, 58, 61, 17, 3, 5, 74, 83, 90, 6];
$N = 6; // number of unique indices to pick
// Get unique random indices
$indices = pick_unique_indices(count($data), $N);
// Print results
echo "Random unique indices and their values:\n";
foreach ($indices as $idx) {
echo "index $idx -> value {$data[$idx]}\n";
}
/*
run:
Random unique indices and their values:
index 10 -> value 17
index 3 -> value 19
index 16 -> value 6
index 4 -> value 5
index 9 -> value 61
index 8 -> value 58
*/
