Assignment to array element reference does not count as a write

[sirbrillig]

static function dotToMultiArray(
	array $array
): array {
	$multi = [];
	foreach($array as $key => $value){
		$level = &$multi;
		foreach(explode(".", $key) as $node)
			$level = &$level[$node];
		$level = $value;
	}
	return $multi;
}

This marks $level as unused but the third assignment actually changes the referenced variable.