PHP получаю Call to a member function fetch_all() on boolean при запросе через js fetch

Пожалуйста, помогите! Ничего не понимаю... Вроде, должно все работать.

Спрашиваю с помощью js у сервера:

request({url, data}) {
        return fetch(url, {
            method: 'POST',
            cache: 'no-cache',
            credentials: 'same-origin',
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded',
            },
            redirect: 'follow',
            referrer: 'no-referrer',
            body: data,
        })
        .then(response => response.text());
    }

На стороне сервера меня ждут вот с таким:

<?php
require_once(__DIR__.'/../classes/Connection.php');
require_once(__DIR__.'/../classes/JSONRewriter.php');
require_once(__DIR__.'/../classes/Purify.php');
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $referrer = POST ...;
    $real_row = ...;
    $newConnection = new Connection();
    $overwriting = Purify::openArray($newConnection->getFromDB(sql-хрень));
    if () {
        ...Обработка результата...
    }
    $newConnection->query(Запись результата);
}

Класс для подключения

class Connection {
    private $host = ...;
    private $user = ...;
    private $pswd = ...;
    private $dbse = ...;
    public function con() {
        $connect = new mysqli($this->host, $this->user, $this->pswd, $this->dbse);
        if ($connect->connect_error) throw new Exception('MySQL connection attempt dropped. {$connect->connect_errno}. {$connect->connect_error}');
        return $connect;
    }
    public function query($query) {
        $connect = $this->con();
        mysqli_query($connect, $query);
        mysqli_close($connect);
    }
    public function getFromDB($query) {
        $connect = $this->con();
        $response = mysqli_query($connect, $query);
        return $response->fetch_all($resulttype = MYSQLI_NUM);
        mysqli_close($connect);
    }
}

php работал, пока я спрашивал его через xhr, но на fetch выдает

<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function fetch_all() on boolean in C:\Users\S_iva\OneDrive\Desktop\OSPanel\domains\localhost\api\classes\Connection.php:22
Stack trace:
#0 C:\Users\S_iva\OneDrive\Desktop\OSPanel\domains\localhost\api\set\referrer.php(14): Connection-&gt;getFromDB('SELECT content ...')
#1 {main}
  thrown in <b>C:\Users\S_iva\OneDrive\Desktop\OSPanel\domains\localhost\api\classes\Connection.php</b> on line <b>22</b><br />