Example code for PHP class

student-list.php

<?php
// DATA

$students = [];
$students[] = [
    "name" => "Thomas Mak",
    "class" => "S1A",
    "number" => 32,
    "enrolled_classes" => [
        "Chinese",
        "English",
        "Web Develpment"
    ],
];
$students[] = [
    "name" => "John Ivan",
    "class" => "S1B",
    "number" => 31,
    "enrolled_classes" => [
        "Chinese",
        "English",
        "Web Develpment"
    ],
];
$students[] = [
    "name" => "Susuan Lee",
    "class" => "S1A",
    "number" => 12,
    "enrolled_classes" => [
        "English",
        "Physics",
        "Web Develpment"
    ],
];

// echo "<pre>";
// var_dump($students);

$class = $_POST["class"] ?? "";

?>
<h1>Students</h1>
<ol>
    <?php foreach($students as $student): ?>
        <?php if ($student["class"] == $class): ?>
            <li>
                <strong><?= $student["name"] ?></strong>
                <br>
                <?= $student["class"] ?> <?=$student["number"] ?>
            </li>
        <?php endif; ?>
    <?php endforeach ?>
</ol>

<form action="" method="POST">
  Please choose class to list students:<br>
  <select name="class">
    <option value="S1A">高一信</option> 
    <option value="S1B">高一望</option>
  </select>
  <input type="submit" value="List Students">
</form>