SQL只能插入1个数据

Question

您好我的SQL代码有问题而且我不知道原因是什么。以下是我的代码：

//Sanitize the POST values
    $appdate = clean($con, $_POST['appdate']);
    $apptime = clean($con, $_POST['apptime']);
    $topic = clean($con, $_POST['topic']);
    $evaluation = clean($con, $_POST['evaluation']);
    $counselor = clean($con, $_POST['counselor']);
    $desc = clean($con, $_POST['desc']);

    $sql="INSERT INTO appointment VALUES(NULL, '$memid', '$counselor', '$appdate', '$apptime', '$topic', '$evaluation', '$desc', 'Pending')";
    $test=mysqli_query($con, $sql);

    //Check whether the query was successful or not
    if($test) {
        header("location: main.php?page=appointments");
        exit();
    } else {
        echo "Query failed.";
        exit();
    }

问题是，我只能将1个数据只插入表中。下一个数据无法插入表格中，它将显示＆＃34;查询失败＆＃34;。这对我来说很困惑。有人可以帮助我。

p / s：抱歉语法错误/英语