Challenge 3 — Solution

Task: Given an array of 8 numbers, use array_filter() with an
anonymous function to keep only numbers greater than 10, then use
array_map() on the filtered result to square each remaining number.
Wrap the filtered result in array_values() before mapping, and
print_r the final array.

<?php
    $numbers = [4, 15, 8, 22, 3, 11, 7, 30];

    $filtered = array_filter($numbers, function ($n) {
        return $n > 10;
    });

    $reindexed = array_values($filtered);

    $squared = array_map(function ($n) {
        return $n * $n;
    }, $reindexed);

    print_r($squared);
?>


Output:
Array
(
    [0] => 225
    [1] => 484
    [2] => 121
    [3] => 900
)

Notes:
- array_filter() keeps only 15, 22, 11, and 30 (the values greater than
  10), but leaves them at their original indexes (1, 3, 5, 7) with gaps
  in between, exactly as the chapter's own warn-box describes.
- array_values() closes those gaps, producing a clean, freshly
  re-indexed array (0, 1, 2, 3) before mapping.
- array_map() then squares each of the four remaining numbers,
  producing the final result: 15*15=225, 22*22=484, 11*11=121,
  30*30=900.