跟踪哪些列数据应该进入

Question

Problem

So, I have this program that allows the user to edit student info in the db. When the submit button is clicked on the info goes into an array, so I can easily loop through the info and put the info into the db. But, the problem is that I don't know how to figure out which column the info goes into.

My current method is by using a variable to keep track of the column that the info should go into, but that doesn't work.

I'm my html, I'm putting the student info into an input, so the user can edit the info.

Students Table

studentID | firstname | lastname | teacherID
1         | Bob       | Roberts  | 2
2         | Rick      | Phil     | 1

PHP Form

<form action="server/edit/students.php" method="post">
                <table>
                    <tr>
                        <th>Student ID</th>
                        <th>Firstname</th>
                        <th>Lastname</th>
                        <th>Teacher ID</th>
                    </tr>
                    <?php
                    // get student info
                    $getStudent = $link->prepare("SELECT * FROM students");
                    $getStudent->execute();
                    $getStudent = $getStudent->fetchAll(PDO::FETCH_ASSOC);
                    $value = 0; // counts rows
                    // loop through each student
                    foreach ($getStudent as $student) {
                        $studentID = $student['studentID'];
                        $firstname = $student['firstname'];
                        $lastname = $student['lastname'];
                        $teacherID = $student['teacherID'];

                     ?>

                        <tr>
                            <td>
                                <?php echo $studentID ?>
                            </td>
                            <td>
                                <input type='text' name='student[<?php echo $studentID ?>][firstname]' value='<?php echo $firstname ?>' />
                            </td>
                            <td>
                                <input type='text' name='student[<?php echo $studentID ?>][lastname]' value='<?php echo $lastname ?>' />
                            </td>
                            <td>
                                <input type='text' name='student[<?php echo $studentID ?>][teacherID]' value='<?php echo $teacherID ?>' />
                            </td>
                        </tr>

                        <?php
                            // add to row
                            $value += 1;

                    }
                    ?>
                </table>
                <button type="submit" name="update">Update</button>
            </form>

PHP Code That Process's Form Info

$counter = 0; // keeps track of number of columns

// get data and loop through it
foreach ($_POST['student'] as $id => $data) {
    foreach ($data as $d) {
        if($counter > 1) {
            $counter = 0;

            update($counter, $link, $id, $d);
        } else {
            update($counter, $link, $id, $d);
        }
    }
}

function update($counter, $link, $id, $d) {

    if($counter == 0) {
        $update = $link->prepare("UPDATE students SET firstname = :firstname WHERE studentID = :id");
        $update->execute(array(
            "firstname" => $d,
            "id" => $id
        ));

        echo $counter . "<br>";

        $counter++;
    } else if($counter == 1) {
        $update = $link->prepare("UPDATE students SET lastname = :lastname WHERE studentID = :id");
        $update->execute(array(
            "lastname" => $d,
            "id" => $id
        ));

        echo $counter . "<br>";

        $counter++;
    }

}

Answer 1

The issue is because your $counter variable is not being passed as a reference. Try the following:

function update(&$counter, $link, $id, $d) {

Before, the variable being passed would always equate to 0. When you increment it, the change isn't saved. When you pass by reference using the & sign, it tells PHP to update the variable you originally sent and not a new copy.

Edit: Thanks Bob!