<?php

$data = [1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 0, 0, 0, 100];
$data = [19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31];

$result = [];

foreach($data as $n => $value) {
	$n = ($n % 6) + 1;
	$result["amount$n"] += $value;
}

var_export($result);