Msqli php query update doesn't work, returns no errors

I wrote the following code:

 public static function updateUser($userid, $username){
 $query = 'UPDATE users SET username=? WHERE id=?';
    $statement =  $GLOBALS["DB"]->prepare($query);
    $statement->bind_param('is', $userid, $username);
    $statement->execute();
    $statement->store_result();

    if ($statement->affected_rows == 1){
        return  1;
    }
    else{
        return $statement;
    }}

      

        
        
        
      

    

The table names are correct, the data I pass inside the method is fine too, but it fails and returns no error. When I try to return these instructions to the console, it gives me this:

mysqli_stmt Object ([affected_rows] => 0 [insert_id] => 0 [num_rows] => 0 [param_count] => 2 [field_count] => 0 [errno] => 0 [error] => [error_list] => Array () [sqlstate] => 00000 [id] => 3) {"Status": "Success"}

I checked the error list, it is empty. Do I need to install something to keep it updated? Does anyone have an idea what this might be? The database is created as follows:

<?php
    require_once ("simplecms-config.php");
    require_once ("./Functions/database.php");

    // Create database connection
    $databaseConnection = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
    if ($databaseConnection->connect_error)
    {
        die("Database selection failed: " . $databaseConnection->connect_error);
    }
    // Create tables if needed.
    prep_DB_content();
    $GLOBALS['DB'] = $databaseConnection ;
?>