splat.php

<?php


// rest ... a,b,c,d,e => []
function concatenate($transform, ...$strings) {
  $string = '';
  foreach($strings as $piece) {
    $string .= $piece;
  }
  return($transform($string));
}

echo concatenate("strtoupper", "I'm ", 20 + 2, " years", " old."); // I'M 22 YEARS OLD.


// spread ... []
function add($a, $b, $c) {
    return $a + $b + $c;
}

$operators = [2, 3];
echo add(1, ...$operators); // 6