这次更新有什么问题

Question

以下是我的查询，我用来替换''中的标题，但它仍然保留了Call to a member function bind_param() on a non-object的错误。请告诉我如何

$title = "What is";
$title_id = "123";
$wadb_stmt = $con->prepare("UPDATE table1 SET REPLACE(title, ?, ''), dt_created = now() WHERE title_id = ?");
    $wadb_stmt->bind_param("ss", $title, $title_id); /// ss means only string input is allowed 

    if ($wadb_stmt->execute())
    echo "true";
    else
    echo "falseE".$wadb_stmt->error;