group consecutive values in array with predicate

group-by.php

<?php

$groupBy = function (array $xs, callable $f) {
	reset($xs);
	$r = [];
	$t = [];

	while (array_key_exists(key($xs), $xs)) {
		$x = current($xs);
		$t[] = $x;

		$nx = next($xs);

		if (!array_key_exists(key($xs), $xs) || !$f($x, $nx)) {
			$r[] = $t;
			$t = [];
		}
	}

	return $r;
};

$strictlyEqual = function ($a, $b) {
	return $a === $b;
};

var_dump($groupBy([], $strictlyEqual));
var_dump($groupBy([false], $strictlyEqual));
var_dump($groupBy([false, false, true, false, true, true], $strictlyEqual));
var_dump($groupBy([1, 2, 1], $strictlyEqual));
var_dump($groupBy([1, 2, 2, 3, 3, 4, 5, 6, 6], $strictlyEqual));