CHALL #3

function sumAdjacent($a) {
  $res = 0;
  for($i=1; $i<count($a); $i++) ($res += abs($a[$i]-$a[$i-1]));
  return $res;
}

echo sumAdjacent([4, 7, 1, 2])."<br>";
echo sumAdjacent([1, 5, 10, 4, 2])."<br>";
echo sumAdjacent([1, 1, 1, 1]);