PDO basic example (not tested)

<?php
// Args
$dsn = 'mysql:host=myHostname;dbname=myDbName';
$username = 'some_username';
$password = 'some_password';

// Database, as PDO object
$db = new \PDO($dsn, $username, $password);


// SELECT example
// =============================
// A SELECT query
$sql = 'SELECT name, email FROM users WHERE id = :id';

// Prepare the query
$statement = $db->prepare($sql);
$statement->bindValue(':id', (integer) $_GET['id'], \PDO::PARAM_INT);

// Run
$statement->execute();

// Collect and return the user data, if present
if ($result = $statement->fetch(\PDO::FETCH_ASSOC)) {
    return $result;
}


// INSERT example
// =============================
// An INSERT query
$sql = 'INSERT INTO users (name, email) VALUES (:name, :email)';

// Begin a transaction, to retrieve the last insert id
$db->beginTransaction();

try {
    // Prepare the query
    $statement = $db->prepare($sql);
    $statement->bindValue(':name', (string) $_POST['name'], \PDO::PARAM_STR);
    $statement->bindValue(':email', (string) $_POST['email'], \PDO::PARAM_STR);

    // Run
    $statement->execute();

    // Query to retrieve the last insert id
    $sql = 'SELECT MAX(id) FROM users';

    // Prepare the query
    $statement = $db->prepare($sql);

    // Run
    $statement->execute();

    // Collect the data
    $result = $statement->fetch(\PDO::FETCH_NUM));

    // Commit
    $db->commit();

    // Last ID
    $last_insert_id = $result[0];
} catch (\PDOException $e) {
    // Undo everything
    $db->rollback();

    // Last ID
    $last_insert_id = null;
}