My database is totally utf8mb4_unicode_ci encoded but when I try to echo character with accent mark like è ù... it doesn't print (or "send") anything at all.
PHP API
  ob_start();
  $Connection = new Connection();
  $zones = $Connection->arrCol("SELECT [...]", "column_name");
  ob_end_clean();
  header('Content-Type: application/json; Charset=UTF-8');
  echo json_encode($zones);
that's my function which put mysql table column inside an array
public function arrCol($query, $column)
    {
        if ($result = $this->conn->query($query))
        {
        $n=0;
            while ($row = $result->fetch_assoc())
            { 
            $ar[$n]=$row[$column];
            $n++;
    }
        return $ar;
        }
        else
    {echo "Error: " . $query . "<br>" . $this->conn->error; }
    }