For a given array and a given threshold, return the subarray which contains the longest run of consecutive numbers which - in total - are equal-to or less than the threshold. (see http://blog.adamcameron.me/2014/11/something-for-weekend-wee-code-quiz-in.html)

getSubseries.php

<?php
$threshold = 500;
// Test cases
$tests = [
	// empty array
	[[], []]
	// one element array
	, [[1], [1]]
	// more element array
	, [[1,2,3], [1,2,3]]
	// no result array
	, [[501, 502, 503], []]
	// one result array
	, [[501, 1, 502, 503], [1]]
	// more result array
	, [[501, 1, 2, 502, 503], [1,2]]
	// first result array
	, [[1, 2, 501, 502, 503], [1,2]]
	// last result array
	, [[501, 502, 503, 1, 2], [1,2]]
	// exactly threshold
	, [[501, 499, 502, 499, 1, 502, 503], [499,1]]
	// Adams array
	, [[100, 300, 100, 50, 50, 50, 50, 50, 500, 200, 100], [100, 50, 50, 50, 50, 50]]
];

// run tests
foreach ($tests as $value) {
	if (getSubSeries($value[0], $threshold) !== $value[1]) {
		echo "\n\nError for input\n";
		var_dump($value[0]);
		echo "\n  expected\n";
		var_dump($value[1]);
		echo "\n  got\n";
		var_dump(getSubSeries($value[0], $threshold));
	}
}

function getSubSeries($inputArray, $threshold) {
	$window = [];
	$bestSoFar = [];
	while (sizeof($inputArray) > 0) {
		// add to the window until it breaks
		while(array_sum($window) <= $threshold && sizeof($inputArray) > 0) {
			array_push($window, array_shift($inputArray));
		}
		// if window is longer than bestSoFar, add it 
		if(sizeof($window) > sizeof($bestSoFar)) {
			$bestSoFar = $window;
			// fix breakage
			if(array_sum($bestSoFar) > $threshold) {
				array_pop($bestSoFar);
			}
		}
		// drop elements from window till it is unbroken
		while(array_sum($window) > $threshold) {
			array_shift($window);
		}
	}
	return($bestSoFar);
}

?>