Here is my solution:
<?php
$arr = array_map("floatval", explode(" ", readline()));
for ($i = 0; $i < count($arr) - 1; $i++) {
if ($arr[$i] == $arr[$i + 1]) {
$newElement = $arr[$i] + ($arr[$i + 1]);
array_splice($arr, $i, 2, $newElement);
$i -= 2;
}
}
echo implode(" ", $arr);