array_add.php

<?php

function array_add(&$arr, array $parts, $val = 1)
{
	if (count($parts) > 1)
	{
		if (!isset($arr[$parts[0]]))
		{
			$arr[$parts[0]] = [];
		}

		array_add($arr[$parts[0]], array_slice($parts, 1), $val);
		return;
	}

	if (!isset($arr[$parts[0]]))
	{
		$arr[$parts[0]] = 0;
	}

	$arr[$parts[0]] += $val;
}

$arr = [];

array_add($arr, ["2016-06-01", "clicks", "unique"], 1);
array_add($arr, ["2016-06-01", "clicks", "total"], 1);
array_add($arr, ["2016-06-01", "views", "total"], 1);