Php studentID的查询插入NULL

问题

<div class="add_team">
                <h1>Add Team</h1>

                <form action="server/add/add_team.php" method="post">
                    <input type="text" name="leader_id" placeholder="* Leader ID">
                    <input type="text" name="student_id_1" placeholder="Student ID">
                    <input type="text" name="student_id_2" placeholder="Student ID">
                    <input type="text" name="student_id_3" placeholder="Student ID">
                    <input type="text" name="student_id_4" placeholder="Student ID">
                    <input type="text" name="student_id_5" placeholder="Student ID">
                    <input type="text" name="student_id_6" placeholder="Student ID">

                    <center>
                        <button type="submit" name="Add"><i class="fa fa-plus-circle fa-lg" aria-hidden="true"></i>Add</button>
                    </center>
                </form>
            </div> <!-- END OF .ADD_TEAM -->

我有这个表格，管理员可以输入一个领导id和最多6个学生id。当管理员单击submit按钮时，my PHP文件应该验证输入中的信息，然后在db中输入领导id和学生id。但是当我测试程序时，程序会为学生id插入

NULL

团队表（开始时为空）

PHP代码

<?php 

require '../connect.php';

$leaderID = $_POST['leader-id'];
$students = array(
    $_POST['student-id-1'],
    $_POST['student-id-2'],
    $_POST['student-id-3'],
    $_POST['student-id-4'],
    $_POST['student-id-5'],
    $_POST['student-id-6'],
);

$studentSave = array();

// check if inputs are not empty
if(!empty($leaderID)) {

    // loop through all students
    foreach ($students as $student) {

        // check if student is not empty
        if(!empty($student)) {
            // add student to new array
            array_push($studentSave, $student);
        }

    }

    // loop through all students
    foreach ($studentSave as $student) {
        // check if students exist
        $getStudent = $link->prepare("SELECT * FROM students
                                    WHERE studentID = ':student'");
        $getStudent->execute(array(
            "student" => $student
        ));
        $getStudent->fetch();

        // if student exist
        if($getStudent) {

            // insert them into the database
            $insert = $link->prepare("INSERT INTO teams (leaderID, studentID)
                                    VALUES (:leaderID, :studentID)");
            $insert->execute(array(
                "leaderID" => $leaderID,
                "studentID" => $studentID,
            ));

            if(!$insert) {
                header("Location: ../../admin.php?msg=Sorry, we ran into an error");
            } else {
                header("Location: ../../admin.php?msgSuccess=Success");
            }

        } else {

            header("Location: ../../admin.php?msg=A student doesn't exist");

        }
    }

} else if(empty($leaderID)){
    header("Location: ../../admin.php?msg=There must be a leader");
}
?>

// insert them into the database
            $insert = $link->prepare("INSERT INTO teams (leaderID, studentID)
                                    VALUES (:leaderID, :studentID)");
            $insert->execute(array(
                "leaderID" => $leaderID,
                "studentID" => $student,
            ));

---

我的问题是变量
$studentID
未定义，所以我应该使用
$student

代码

<?php 

require '../connect.php';

$leaderID = $_POST['leader-id'];
$students = array(
    $_POST['student-id-1'],
    $_POST['student-id-2'],
    $_POST['student-id-3'],
    $_POST['student-id-4'],
    $_POST['student-id-5'],
    $_POST['student-id-6'],
);

$studentSave = array();

// check if inputs are not empty
if(!empty($leaderID)) {

    // loop through all students
    foreach ($students as $student) {

        // check if student is not empty
        if(!empty($student)) {
            // add student to new array
            array_push($studentSave, $student);
        }

    }

    // loop through all students
    foreach ($studentSave as $student) {
        // check if students exist
        $getStudent = $link->prepare("SELECT * FROM students
                                    WHERE studentID = ':student'");
        $getStudent->execute(array(
            "student" => $student
        ));
        $getStudent->fetch();

        // if student exist
        if($getStudent) {

            // insert them into the database
            $insert = $link->prepare("INSERT INTO teams (leaderID, studentID)
                                    VALUES (:leaderID, :studentID)");
            $insert->execute(array(
                "leaderID" => $leaderID,
                "studentID" => $studentID,
            ));

            if(!$insert) {
                header("Location: ../../admin.php?msg=Sorry, we ran into an error");
            } else {
                header("Location: ../../admin.php?msgSuccess=Success");
            }

        } else {

            header("Location: ../../admin.php?msg=A student doesn't exist");

        }
    }

} else if(empty($leaderID)){
    header("Location: ../../admin.php?msg=There must be a leader");
}
?>

// insert them into the database
            $insert = $link->prepare("INSERT INTO teams (leaderID, studentID)
                                    VALUES (:leaderID, :studentID)");
            $insert->execute(array(
                "leaderID" => $leaderID,
                "studentID" => $student,
            ));

fetch
将值提取到某个变量，我假设，第二，您的占位符
：student'
将不起作用。您应该会得到一大堆未定义的索引通知。您使用的变量
$studentID
从未定义过，这就是它插入NULL的原因。您可能需要
$student
。连字符！=下划线和vice versaI发现很难相信这是代码中唯一的错误。