How do I pass a row from a query to use in another query?

Question

I am working on a website that allows someone to log in as an instructor user.

<table border = "1" class = "query">
    <tr>
        <td style = "text-align: center" class = "label-left">
            Classes you are taking
        </td>
        <td style = "text-align: center" class = "label-right">
            Students in each class
        </td>
    </tr>
    <tr>
        <td class = "r1">
            <?php
                $query = "SELECT
                Course.course_Name,
                Course.dept_ID,
                Course.course_Credit,
                Class.CRN,
                Class.course_ID,
                Semester.semester_Name,
                Class.room_ID,
                Class.seat_Avail,
                Building.building_Name
                from Class
                INNER JOIN Semester ON Semester.semester_ID = Class.semester_ID
                INNER JOIN Course ON Class.Course_ID = Course.Course_ID
                INNER JOIN Room ON Class.Room_ID = Room.Room_ID
                INNER JOIN Building on Room.Building_ID = Building.Building_ID 
                INNER JOIN Login ON class.faculty_ID = login.user_ID 
                WHERE login.User_Email = '$_SESSION[user_Email]'";
                $result = $pdo->query($query);
                while ($row = $result->fetch())
                {
                    echo "Course: " . $row['course_Name'] . "<br>"
                    . "Department: " . $row['dept_ID'] . "<br>" 
                    . "Credit(s): " . $row['course_Credit'] . "<br>" 
                    . "CRN: " . $row['CRN'] . "&nbsp&nbsp&nbsp&nbsp" 
                   . '<form action = "view_Faculty_Schedule_&_Students.php" method = "POST"> <input type = "submit" class = "crn-btn" name = "crn_btn" value = "See Students"><input type = "hidden" value = "'.$row['CRN'].'" name = "crn"></form><br>'
                    . "Course ID: " . $row['course_ID'] . "<br>"           //Problem on the line above
                    . "Semester: " . $row['semester_Name'] . "<br>"
                    . "Location: " . $row['room_ID'] . "<br>"
                    . "Seats Available: " . $row['seat_Avail'] . "<br>"
                    . "Building: " . $row['building_Name'] . "<br><br><br>";
                }
                $crn = $_POST['crn'];
                echo $crn;
            ?>
        </td>
        <td style = "vertical-align: top" class = "r2">
            <?php
                if(isset($_POST["crn_btn"]))
                {
                    $query = "SELECT
                    user.user_ID,
                    login.user_Email,
                    user.first_Name,
                    user.last_Name,
                    student_history.Grade
                    FROM student_history
                    INNER JOIN class ON class.CRN = student_history.CRN
                    INNER JOIN user ON user.user_ID = student_history.student_ID
                    INNER JOIN login ON login.user_ID = user.user_ID
                    WHERE class.CRN = $crn";
                    while ($row = $result->fetch())
                    {
                        echo "ID: " . $row['user_ID'] . "<br>"
                        . "Email: " . $row['user_Email'] . "<br>" 
                        . "First name: " . $row['first_Name'] . "<br>"
                        . "Last name: " . $row['last_Name'] . "<br>"
                        . "Grade: " . $row['Grade'] . "<br><br><br>";
                    }
                }
            ?>
        </td>
    </tr>
</table>

The first query gives the results of all the classes they're taking along with a button next to each 'CRN' row returned. The second query is supposed to return all the students that are taking a specific class depending on which CRN button is clicked. The button seems to work with simple print statements but not the query. I am not sure what the error in my code is or what I'm missing.

How do I pass a row from a query to use in another query?

0 Answers0