将mysqli传递给类不会显示结果

Question

I have problem passing mysqli to my class. It works fine when it's passing to non-class. I tried to use Dependency injection here but for some reason it won't show results when printed, it's just a blank page.

Here is my connect.php

   <?php
$db = new mysqli('localhost', 'root', '', 'audiologiska_kliniken');

if($db->connect_errno > 0){
    die('Ett fel inträffade [' . $db->connect_error . ']');
}

My test class:

   <?php
    //error_reporting(0);
    include '../include/connect.php';


    class test
    {
        private $mysqli;

        function __construct(mysqli $db)
        {
            $this->mysqli = $db;
            $this->testing();
        }
        function testing()
        {
            $result = $this->mysqli->query("Select * from person");
                print_r($result);
        }
    }

Answer 1

you are not instantiating test in order to use it

include '../include/connect.php';

class test
{
    private $mysqli;

    function __construct(mysqli $db)
    {
        $this->mysqli = $db;
        $this->testing();
    }
    function testing()
    {
        $result = $this->mysqli->query("Select * from person");
            print_r($result);
    }
}

new test($db);