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You've done the hard work already. Instead of calculating the product, store the selected array. <?php $primes = array(2, 3, 5, 7, 11, 13, 17, 19, 23); $combos = []; function getAllCombinations($arr, $n, &$combos, $selected = array(), $startIndex = 0) { if ($n == 0) { $combos[] = $selected; // $product = 1; // foreach ($selected as $prime) { // $pr[] = $prime; // $product *= $prime; // $pr[] = $prime; // } // echo "Product: $product\n"; return; } for ($i = $startIndex; $i < count($arr); $i++) { $selected[] = $arr[$i]; getAllCombinations($arr, $n - 1, $combos, $selected, $i + 1); array_pop($selected); // Backtrack and remove the element for next iteration } } getAllCombinations($primes, 4, $combos); echo '<pre>'; foreach ($combos as $com) { printf("%-35s = %5d<br>", join(' &times; ', $com), array_product($com)); // output numbers and product } ?> giving 2 × 3 × 5 × 7 = 210 2 × 3 × 5 × 11 = 330 2 × 3 × 5 × 13 = 390 2 × 3 × 5 × 17 = 510 2 × 3 × 5 × 19 = 570 2 × 3 × 5 × 23 = 690 2 × 3 × 7 × 11 = 462 2 × 3 × 7 × 13 = 546 2 × 3 × 7 × 17 = 714 2 × 3 × 7 × 19 = 798 2 × 3 × 7 × 23 = 966 2 × 3 × 11 × 13 = 858 2 × 3 × 11 × 17 = 1122 2 × 3 × 11 × 19 = 1254 2 × 3 × 11 × 23 = 1518 2 × 3 × 13 × 17 = 1326 2 × 3 × 13 × 19 = 1482 2 × 3 × 13 × 23 = 1794 2 × 3 × 17 × 19 = 1938 2 × 3 × 17 × 23 = 2346 2 × 3 × 19 × 23 = 2622 2 × 5 × 7 × 11 = 770 2 × 5 × 7 × 13 = 910 . . 5 × 17 × 19 × 23 = 37145 7 × 11 × 13 × 17 = 17017 7 × 11 × 13 × 19 = 19019 7 × 11 × 13 × 23 = 23023 7 × 11 × 17 × 19 = 24871 7 × 11 × 17 × 23 = 30107 7 × 11 × 19 × 23 = 33649 7 × 13 × 17 × 19 = 29393 7 × 13 × 17 × 23 = 35581 7 × 13 × 19 × 23 = 39767 7 × 17 × 19 × 23 = 52003 11 × 13 × 17 × 19 = 46189 11 × 13 × 17 × 23 = 55913 11 × 13 × 19 × 23 = 62491 11 × 17 × 19 × 23 = 81719 13 × 17 × 19 × 23 = 96577

1. If you use /s for regex delimiters (at the beginning and end) then any /s you want inside the regex have to be escaped. Look at what your original had. 2. What's the rest of the code?

Why would you use Javascript for this? It's okay to have the regex be multiple patterns. You don't, not necessarily, have to use a single capture group to get the one value you care about. youtube.com/shorts/(\w+)|youtube.com/watch\?v=(\w+)|youtu.be/whatever else Only one of $1 or $2 (or what you put in the "whatever else") will ever have a value. And do remember that "." matches anything, so "youtubexcom/short/blah" will match the above too.