I am urgently seeking assistance with the following error:
Commands out of sync; you can't run this command now

here's the code:

$sql="select pr1.".$_SESSION['lang'].", pr1.id, pr2.".$_SESSION['lang'].", pr2.id from `project` as pr2 join project as `pr1` on(pr1.id=pr2.parent_project) where pr2.id=?";
        $stmt = $mysqli->stmt_init();   
        $stmt->prepare($sql) or die ("Error preparing statement: ".$mysqli->error);
        $stmt->execute() or die("Error, error, error!");

I have tied non prepared statements (they work...) and have even changed the sql to something simple without binding parameters, but as soon as I get to the ececute statement the error is triggered.

Thanks in advance!