Евгений Антипов

let $data = new FormData($(this).get(0));
$.ajax({
                url: "form.php",
                type: "POST",
                data: $data,
                dataType: "JSON",
                processData: false,
                contentType: false,
                cache: false,
                async: true
            });

$route->onHttpError(
            function ($code) {
                $instance = "frontend\\controllers\\Home";
                switch ($code) {
                    case 404:
                    case 405:
                        header("HTTP/1.1 404 Not Found");
                        call_user_func([new $instance, "error404"], self::$answer[0][1]);
                        break;
                    case 403:
                        header("HTTP/1.1 403 Forbidden");
                        call_user_func([new $instance, "error403"], self::$answer[0][1]);
                        break;
                }
        }
 );

function r_array_search($needle, $haystack, $currentKey = "") {
    foreach ($haystack as $key => $value) {
        if (is_array($value)) {
            $nextKey = r_array_search($needle, $value, $currentKey . "[{$key}]");            
            if ($nextKey) {
                return $nextKey;
            }
        } else if ($value == $needle) {
            return is_numeric($key) ? $currentKey . "[{$key}]" : $currentKey . "['{$key}']";
        }
    }
    return false;
}

$GLOBAL = [
    3515 => [
        'sub_categories' => [
            22916 => [
                'sub_categories' => [
                    33221 => 'test'
                ]
            ],
        ]
    ],
    35215 => [
        'sub_categories' => [
            221916 => 'test2'
        ]
    ],
];

print_r(r_array_search("test", $GLOBAL));

//[3515][sub_categories][22916][sub_categories][33221]

$array = [1 => "one", 2 => "two", 4 => "four", 5=> "five", 6 => "six"];
$array = array_chunk($array, count($array)/2);
$first = array_shift($array);
$second = array_reduce($array , "array_merge", []);

в математике полный ноль