find-next-item.php

<?php

function array_to_entries(array $array) {
	return array_map(function ($key, $value) {
		return [
		    "key" => $key,
		    "value" => $value,
		];
	}, array_keys($array), array_values($array));
}

function findNextItem(array $input, $currentKey, $loop = false) {
    return array_reduce(array_to_entries($input), function (array $context, $item) use ($currentKey){
        return [
            "isCurrent" => $item["key"] === $currentKey,
            "value" => $context["isCurrent"] ? $item["value"] : $context["value"],
        ];
    }, [
        "isCurrent" => false,
        "value" => $loop ? reset($input) : null,
    ])["value"];
}

function findPrevItem(array $input, $currentKey, $loop = false) {
	return findNextItem(array_reverse($input), $currentKey, $loop);
}




var_dump(
	findNextItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'alpha') === 2,
	findNextItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'bravo') === 3,
	findNextItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'charlie') === null,
	findNextItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'charlie', true) === 1,
	findNextItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'not found') === null,

	findPrevItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'alpha') === null,
	findPrevItem(['alpha' => 1, 'bravo' => 2, 'charlie' => 3], 'alpha', true) === 3
	
);