Prepared Statements in PHP for CRUD

crud.php

<?php
$servername = "localhost";
$username = "root";
$password = " ";
$dbname = "demo";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
/* ------------------------------------------------------------------------------------------------------------------------------------------ */
/*
    Binds variables to prepared statement

    i    corresponding variable has type integer
    d    corresponding variable has type double
    s    corresponding variable has type string
    b    corresponding variable is a blob and will be sent in packets
 */
/* ------------------------------------------------------------------------------------------------------------------------------------------ */

// Insert data
$stmt = $conn->prepare("INSERT INTO `myguests`(`firtname`, `lastname`, `email`) VALUES ( ?, ?, ?)");
$stmt->bind_param("sss", $firstname, $lastname, $email);

// insert a row
$firstname = "John";
$lastname = "Doe";
$email = "john@example.com";
$stmt->execute();

echo "New records created successfully <br><br>";
$stmt->free_result();
$stmt->close();
/* ------------------------------------------------------------------------------------------------------------------------------------------ */

// Update data
$stmt2 = $conn->prepare("UPDATE `myguests` SET `firtname`=?,`lastname`=?,`email`=? WHERE `id`=?");
$stmt2->bind_param("sssi", $firstname, $lastname, $email, $id);

// update a row
$firstname = "Johnny";
$lastname = "Depp";
$email = "jon@depp.com";
$id = 8;
$stmt2->execute();

echo "Records updated successfully <br><br>";
$stmt2->free_result();
$stmt2->close();
/* ------------------------------------------------------------------------------------------------------------------------------------------ */

//Display the result
$stmt1 = $conn->prepare("SELECT * FROM `myguests`");
//$stmt1->bind_param('s', $id);
$stmt1->execute();
$stmt1->bind_result($id, $firstname, $lastname, $email);
$stmt1->store_result();

if ($stmt1->num_rows() > 0) {
    while ($stmt1->fetch()) {
        echo $id . ") " . $firstname . " " . $lastname . " " . $email . "<br><br>";
    }
}

$stmt1->free_result();
$stmt1->close();
/* ------------------------------------------------------------------------------------------------------------------------------------------ */

//Delete the result
$stmt3 = $conn->prepare("DELETE FROM `myguests` WHERE `id`=?");
$stmt3->bind_param('i', $id);
$id = 16;
$stmt3->execute();

$stmt3->free_result();
$stmt3->close();
/* ------------------------------------------------------------------------------------------------------------------------------------------ */
$conn->close();