Retrieving the ID with the lastInsertId() Method

The lastInsertId() method returns the ID of the last inserted row or a sequence value automatically generated by the database (typically via AUTO_INCREMENT). This is crucial in situations where, after inserting data into one table, you need this unique ID to link with other tables in the database. The method operates directly on the connection object rather than on a prepared statement.

EXAMPLE

<?php
class Database {
    private $server = "localhost";
    private $username = "root";
    private $password = "";
    private $db_name = "pdo_db";
    public $connection;

    public function __construct() {
        try {
            // Added charset=utf8mb4 for character support
            $dsn = "mysql:host=" . $this->server . ";dbname=" . $this->db_name . ";charset=utf8mb4";
            $this->connection = new PDO($dsn, $this->username, $this->password);
            $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch(PDOException $e) {
            die("Connection failed: " . $e->getMessage());
        }
    }

    public function addAndReturnId($first_name, $last_name, $email) {
        $sql = "INSERT INTO users (first_name, last_name, email) VALUES (:first_name, :last_name, :email)";
        $statement = $this->connection->prepare($sql);
        $statement->execute(['first_name' => $first_name, 'last_name' => $last_name, 'email' => $email]);

        // Retrieve the ID assigned by the database
        return $this->connection->lastInsertId();
    }
}

// PART 3: Usage
$db = new Database();
$new_id = $db->addAndReturnId('Borut', 'Bukovnik', 'admin@example.com');

echo "New user was added under number (ID): " . $new_id;
?>

RESULT

The result will be displayed here...

Practical Application: We call this method immediately after a successful INSERT command. If the insertion was unsuccessful or if the table does not have automatic key generation enabled, the method will return 0 or the string "0". Check the process at home by following these steps:

Start the Apache and MySQL modules in the XAMPP control panel.
Ensure that the users table has its id column set to AUTO_INCREMENT.
The method returns the ID as a string, representing the number of the last record.
Insert the example below into a PHP file and see which number the new user will receive.