<?php
$conn = mysqli_connect("localhost", "root", "", "student_db");

$id = $name = $stage = $age = "";

if (isset($_POST['show'])) {
    $id = $_POST['id'];
    $result = mysqli_query($conn, "SELECT * FROM students WHERE id = '$id'");
    if ($row = mysqli_fetch_assoc($result)) {
        $name = $row['full_name'];
        $stage = $row['stage'];
        $age = $row['age'];
    }
}

if (isset($_POST['save'])) {
    $id = $_POST['id']; $name = $_POST['full_name']; $stage = $_POST['stage']; $age = $_POST['age'];
    $check = mysqli_query($conn, "SELECT * FROM students WHERE id = '$id'");
    if (mysqli_num_rows($check) > 0) {
        echo "<script>alert('Error: ID $id already exists!');</script>";
    } else {
        mysqli_query($conn, "INSERT INTO students VALUES ('$id', '$name', '$stage', '$age')");
    }
}

if (isset($_POST['update'])) {
    $id = $_POST['id']; $name = $_POST['full_name']; $stage = $_POST['stage']; $age = $_POST['age'];
    mysqli_query($conn, "UPDATE students SET full_name='$name', stage='$stage', age='$age' WHERE id='$id'");
}

if (isset($_POST['delete'])) {
    $id = $_POST['id'];
    mysqli_query($conn, "DELETE FROM students WHERE id = '$id'");
    $id = $name = $stage = $age = "";
}
?>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Student Details</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body class="p-5 bg-light">

<div class="container bg-white p-4 border shadow-sm" style="max-width: 900px;">
    <h4 class="mb-4">Student Details</h4>

    <table class="table table-sm mb-4">
        <thead>
            <tr class="text-muted small">
                <th>ID</th>
                <th>Full Name</th>
                <th>Stage</th>
                <th>Age</th>
            </tr>
        </thead>
        <tbody>
            <?php
            $all = mysqli_query($conn, "SELECT * FROM students");
            while($row = mysqli_fetch_assoc($all)) {
                echo "<tr>
                        <td>{$row['id']}</td>
                        <td>{$row['full_name']}</td>
                        <td>{$row['stage']}</td>
                        <td>{$row['age']}</td>
                      </tr>";
            }
            ?>
        </tbody>
    </table>

    <hr>

    <form method="POST">
        <div class="row g-2">
            <div class="col-md-2">
                <input type="text" name="id" class="form-control" placeholder="ID" value="<?php echo $id; ?>">
            </div>
            <div class="col-md-4">
                <input type="text" name="full_name" class="form-control" placeholder="Name" value="<?php echo $name; ?>">
            </div>
            <div class="col-md-3">
                <input type="text" name="stage" class="form-control" placeholder="Stage" value="<?php echo $stage; ?>">
            </div>
            <div class="col-md-3">
                <input type="text" name="age" class="form-control" placeholder="Age" value="<?php echo $age; ?>">
            </div>
        </div>

        <div class="mt-4 d-flex gap-2">
            <button type="submit" name="show" class="btn btn-primary px-4">Show</button>
            <button type="submit" name="save" class="btn btn-dark px-4">Save</button>
            <button type="submit" name="update" class="btn btn-dark px-4">Update</button>
            <button type="submit" name="delete" class="btn btn-secondary px-4">Delete</button>
        </div>
    </form>
</div>

</body>
</html>

<!-- 
CREATE DATABASE student_db;
USE student_db;

CREATE TABLE students (
    id INT PRIMARY KEY,
    full_name VARCHAR(100),
    stage VARCHAR(50),
    age INT
);

INSERT INTO students VALUES 
(1, 'Ahmed Saman', 'Second', 20), 
(2, 'Zanyar', 'Fourth', 24),
(3, 'Amanj Jamal', 'second', 22); -->