assign data from one table to a specific table (group) - php

Question

I have a classrooms in schools and when I click on a certain classroom, I want to add students into it but my actual code is doing something stupid. It adds a student but i can see the student in all classrooms, not just in the one that i added him into. So when Im in classroom number 1, I see a form in there, I can add a student there, ... see how it works here:
here is the code: http://www.xxxx.xx/projekt/
here is my code in file trieda.php
<table align="center"><tr><td>
<form action="vlozit2.php" method="post">
Meno: <input type="text" name="meno" placeholder="Janko" maxlength="15" required>
Priezvisko: <input type="text" name="priezvisko" placeholder="Hruška" maxlength="20" required>
<input type="hidden" name="id_triedy" value="<?= $trieda['id_triedy'] ?>" />
<input type="submit" name="submit" value="Pridať študenta do triedy">
</form>
</td></tr></table>
<?php
$result = mysqli_query($prip,"SELECT * FROM student ORDER BY meno");
while($student = mysqli_fetch_array($result))
{
echo "<br /><table cellspacing='1' cellpadding='1' class='tabulka1' align='center'><tr>";
echo "<td width='200'><a href='student.php?id_triedy=".$trieda['id_triedy']."".id_student=".$student['id_student']."'>".$student['meno']." ".$student['priezvisko']."</a></td>";
?>
<td width='300px' align='right' bgcolor="#fbfbfb">Zmazať</td>
</tr></table>
<?php
}
?>
here is vlozit2.php (a code that works for the form to add a student)
if(isset($_POST['submit']))
{
//meno a priezvisko
$student = $_POST['meno'];
$student = $_POST['priezvisko'];
$trieda = $_POST['id_triedy'];
//connect to the database
include 'config.php';
//insert results from the form input
$sql = "INSERT INTO student (meno, priezvisko, id_triedy) VALUES('$_POST[meno]', '$_POST[priezvisko]', '$_POST[id_triedy]')";
$add = "<table align='center'>
<tr>
<td> Študent bol úspešne pridaný do triedy. </td>
</tr>
<tr>
<td><a href='./trieda.php'><strong>Späť</strong></a></td>
</tr>
</table>";
$not_add = "<table align='center'>
<tr>
<td> Študent s týmto menom a priezviskom už je v tejto triede. </td>
</tr>
<tr>
<td><a href='./trieda.php'><strong>Späť</strong></a></td>
</tr>
</table>";
if (mysqli_query($prip, $sql)) {
echo $add;
}else{
echo $not_add;
}
mysqli_close($prip);
}
?>

Answer 1

Try to replace your part of code with these snipets:
1) in trieda.php
<form action="vlozit2.php?id_triedy=<?php echo $_GET["id_triedy"];?>" method="post">
Meno: <input type="text" name="meno" placeholder="Janko" maxlength="15" required>
Priezvisko: <input type="text" name="priezvisko" placeholder="Hruška" maxlength="20" required>
<input type="submit" name="submit" value="Pridať študenta do triedy">
</form>
2) in vlozit2.php
$student = $_POST['meno'];
$priezvisko = $_POST['priezvisko'];
$id_trieda = $_GET['id_triedy'];
and
$sql = "INSERT INTO student (meno, priezvisko, id_triedy) VALUES( '{$student}', '{$priezvisko}', {$id_trieda} )";
Hopefully you store your id_trieda as INT type.

Answer 2

In your vlozit2.php file is nothing about inserting of class id. So put
<input type="hidden" name="classId" value="<?= $trieda['id'] ?>" />
to your form and in vlozit2.php get this value from $_POST['classId'] and insert it with other students data or anywhere you want to have it.