There are several issues with the code snippet you've posted but to make it work again you should fix your error message.

From this:

@is_uploaded_file($_FILES[$image_fieldname]['tmp_name']) 
or redirectToError('<pre>',"Ты в норме? Зачем ты это пытался загрузить? 
Запрос на отправку: файл назывался " , "{$_FILES[$image_fieldname]['tmp_name']}", '</pre>');

To this:

@is_uploaded_file($_FILES[$image_fieldname]['tmp_name']) 
or redirectToError('<pre>',"Ты в норме? Зачем ты это пытался загрузить? Запрос на отправку: файл назывался " , "{$_FILES[$image_fieldname]['tmp_name']}", '</pre>');

Why does your original error message don't work? There is a new line between "Зачем ты это пытался загрузить?" and "Запрос на отправку" in your original error message. Now, based on redirectToError function definition, second parameter will be passed directly to header function without any transformation/encoding. It means, you will pass a multi-line string to as a single HTTP header, which is HTTP protocol violation.

Regarding other PHP Notices, they are shown because no POST data were sent to the page. You can add some very basic check to make sure your script is invoked by form submit:

<?php
if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    // вернуть пользователя обратно на страницу формы
    header("Location: create_user.html");
}


$link = require_once ('../stack/scripts/database_connection.php');
...