Q:

PHP MySQLi query returns NULL

I am trying to get my PHP code to connect to my database hosted on the same server, but no matter what I do, it always ends up returning an empty set. 
$servername = "localhost";
                $username = "user";
                $password = "pass";
                $dbnom = "name";

                $conn = new mysqli($servername, $username, $password, $dbnom);

                mysqli_set_charset($conn, "utf8");

                if(!$conn) {
                    die("La connexion a échoué : " .  mysqli_connect_error());
                }

                $championsSQL = "SELECT pa_championId FROM participants";
                $resultSQL = mysqli_query($conn, $championsSQL);

                if(mysqli_num_rows($resultSQL) > 0) {
                    while($row = mysqli_fetch_assoc($resultSQL)) {
                        echo "Nom des champions : " .  $row["pa_championId"] . " <br>";
                    }
                }
                else {
                    echo "Aucun résultat";
                }
                var_dump($resultSQL);
                mysqli_close($conn);

The MySQL request "SELECT pa_championId FROM participants" works when I enter it manually into the mysql command line on the server. 
The var_dump at the end always returns NULL. 
The PHP is from the "Select Data With MySQLi section of this website : https://www.w3schools.com/php/php_mysql_select.asp
I know this question has been posted many times before, but none of the answers I found fit my exact situation. 
Logs : https://pastebin.com/M2GCQe4D

A:

My best guess is that the connection failed but your $conn wasn't empty so it never enteres this condition:
if(!$conn) {
     die("La connexion a échoué : " .  mysqli_connect_error());
}

You should try using this to see if it returned any errors
if ($conn->connect_error) {
    die("La connexion a échoué : " .  $conn->connect_error);
}

