MySQL查询返回零，并且数据库未更新

Question

我想通过从表单获取值来更新MySQL数据库中的一行，并使用update语句将表单值设置为数据库。问题是执行MySQL查询没有任何错误，但是rowCount()方法返回零，当我通过PHPMyAdmin检查数据库时，它不受影响。这是代码：

elseif(@$do== 'Update'){
    echo "<div class='container'>";
    echo "<h1 class='text-center'>Update</h1>";
    if($_SERVER['REQUEST_METHOD']=='POST'){
        //get variables from the form
        $id          = $_POST['catid'];  
        $mname        = $_POST['name'];
        $mdescription = $_POST['description'];
        $mordering    = $_POST['ordering'];
        $mvisibility  = $_POST['visibility'];  
        $mcommenting  = $_POST['commenting'];
        $mads         = $_POST['ads'];
        $mordering    = $_POST['ordering'];

        $stmt = $con->prepare("UPDATE categories SET Name=?,Description=?,Ordering=? ,Visibility=?,Allow_Comments=? ,Allow_Ads=? WHERE ID=?");           
        $stmt->execute(array($mname,$mdescription,$mordering,$mvisibility,$mcommenting,$mads,$id));
        //echo success message
        echo '<div class="alert alert-success">'.$stmt->rowCount().'Record updated </div>';
    }
    else{
        echo'<div class= "alert alert-danger">sorry you cant browsethis page directly</div>';

    }      
    echo "</div>";  
}

我想念什么？