无法访问数据库中给出的所有元素

Question

这是代码。它完美地显示了我想要的所有元素。但是当我点击“注册”时，它只为任何选定的元素注册一个元素。可能的问题是什么？

以下是代码：

if(array_key_exists("id", $_SESSION)) {

    include("connection.php");
    $query = "SELECT * from `classes`";       

    echo '<div id="accordion" role="tablist" aria-multiselectable="true"> ';

    $result = mysqli_query($link, $query);
    $results = array();

    $rows = array();
    $queries = array();

    while($row = mysqli_fetch_array($result)) {
        array_push($rows, $row);
    }

    for ($i = 0; $i < count($rows); $i ++) {

        $name = $rows[$i]["name"];
        $start_time = $rows[$i]["begTime"];
        $end_time = $rows[$i]["endTime"];

        $price = $rows[$i]["price"];
        $places = $rows[$i]["placesAvailable"];

        if (array_key_exists("enroll", $_POST)) {
            $queries[$i] = "UPDATE `users` SET sectionID = ".$rows[$i]["ID"]." WHERE id = ".mysqli_real_escape_string($link, $_SESSION['id'])." LIMIT 1";

            $results[$i] = mysqli_query($link, $queries[$i]);             
        }

        echo '
            <div  class="card">
                <div id = "section" class="card-header" role="tab" id="headingOne">
                    <h5 class="mb-0">
                        <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
                            '.$name.'
                        </a>
                    </h5>
                </div>

                <div id="collapse" class="collapse in" role="tabpanel" aria-labelledby="headingOne">
                    <div class="card-block">
                    '.$name.'
                        <p> <strong> Time: </strong>'.$start_time.' - '.$end_time.' </p>
                        <p> <strong> Price: </strong>'.$price.' </p>
                        <p> <strong> Places available: </strong>'.$places.' </p>
                        <form action="" method = "post">
                            <input class="btn btn-success" type="submit" name = "enroll" value = "Enroll">
                        </form>
                    </div>
                </div>
            </div>            
        ';
    }
    echo '</div>';
}

Answer 1

您的逻辑不太正确，因为您没有将所需的课程ID与提交的enroll按钮一起发送到脚本。 我已经调整了你的代码。 只有当您的用户/学生当时只能注册一门课程时，此逻辑才有效。

if(array_key_exists("id", $_SESSION)) {

include("connection.php");

        if (array_key_exists("enroll", $_POST)) {
            $query = "UPDATE `users` SET sectionID = ".mysqli_real_escape_string($link, $_POST["ID"])." WHERE id = ".mysqli_real_escape_string($link, $_SESSION['id'])." LIMIT 1";

            mysqli_query($link, $query); 
        }


    $query = "SELECT * from `classes`";


    echo '<div id="accordion" role="tablist" aria-multiselectable="true"> ';

    $result = mysqli_query($link, $query);

    while($row = mysqli_fetch_array($result)) {

        $name = $row["name"];

        $start_time = $rows["begTime"];

        $end_time = $rows["endTime"];

        $price = $rows["price"];

        $places = $rows["placesAvailable"];



        echo '

            <div  class="card">
                <div id = "section" class="card-header" role="tab" id="headingOne">
                    <h5 class="mb-0">
                        <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
                            '.$name.'
                        </a>
                    </h5>
                </div>

                <div id="collapse" class="collapse in" role="tabpanel" aria-labelledby="headingOne">
                    <div class="card-block">
                    '.$name.'
                        <p> <strong> Time: </strong>'.$start_time.' - '.$end_time.' </p>
                        <p> <strong> Price: </strong>'.$price.' </p>
                        <p> <strong> Places available: </strong>'.$places.' </p>
                        <form action="" method = "post">
                            <input type="hidden" name="ID" value="'.$row["ID"].'" />
                            <input class="btn btn-success" type="submit" name = "enroll" value = "Enroll">
                        </form>
                    </div>
                </div>
            </div>

        ';
    }

    echo '</div>';

}

<强>更新 要让用户选择多个课程，您只需要一个带有复选框数组的表单。您的$_POST["ID"]将是一个类ID的数组。在下面的示例中，它被序列化存储在您的数据库中，假设sectionID是字符串。在将数组保存到数据库之前，您还可以json_encode数组。如果您希望sectionID为数字，则需要创建一个新表来存储每个用户的所有类。

if(array_key_exists("id", $_SESSION)) {

include("connection.php");

        if (array_key_exists("enroll", $_POST)) {
            $query = "UPDATE `users` SET sectionID = ".mysqli_real_escape_string($link, serialize($_POST["ID"]))." WHERE id = ".mysqli_real_escape_string($link, $_SESSION['id'])." LIMIT 1";

            mysqli_query($link, $query); 
        }


    $query = "SELECT * from `classes`";


    echo ' <form action="" method = "post">
          <div id="accordion" role="tablist" aria-multiselectable="true"> ';

    $result = mysqli_query($link, $query);

    while($row = mysqli_fetch_array($result)) {

        $name = $row["name"];

        $start_time = $rows["begTime"];

        $end_time = $rows["endTime"];

        $price = $rows["price"];

        $places = $rows["placesAvailable"];



        echo '

            <div  class="card">
                <div id = "section" class="card-header" role="tab" id="headingOne">
                    <h5 class="mb-0">
                        <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="true" aria-controls="collapseOne">
                            '.$name.'
                        </a>
                    </h5>
                </div>

                <div id="collapse" class="collapse in" role="tabpanel" aria-labelledby="headingOne">
                    <div class="card-block">
                    '.$name.'
                        <p> <strong> Time: </strong>'.$start_time.' - '.$end_time.' </p>
                        <p> <strong> Price: </strong>'.$price.' </p>
                        <p> <strong> Places available: </strong>'.$places.' </p>

                            <input type="checkbox" name="ID[]" value="'.$row["ID"].'" />Enroll
                    </div>
                </div>
            </div>

        ';
    }

    echo '</div>
    <input class="btn btn-success" type="submit" name = "enroll" value = "Submit">
    </form>';

}