Vérification de syntaxe

<b>Fatal error</b>:  Uncaught Error: Call to undefined method PDOStatement::exec() in /var/www/api/index.php:96
Stack trace:
#0 {main}
  thrown in <b>/var/www/api/index.php</b> on line <b>96</b><br />

<?php
error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

date_default_timezone_set('Europe/Paris');

function random_1($car) {
    $string = "";
    $chaine = "abcdefghijklmnpqrstuvwxyABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    srand((double)microtime()*1000000);
    for($i=0; $i<$car; $i++) {
    $string .= $chaine[rand()%strlen($chaine)];
    }
    return $string;
    }

//
// on traite la variable email
//
$email = $_POST['email'];
echo $email;

if(empty($email))
{
   header("Location: index.php");
   exit;
}

if(strlen($email) < 6 OR strlen($email) > 60)
{
   header("Location: index.php");
   exit;
}

//
// on traite la variable password
//
$password = $_POST['password'];
echo $password;

if(empty($password))
{
   header("Location: index.php");
   exit;
}

if(strlen($password) < 8 OR strlen($password) > 64)
{
   header("Location: index.php");
   exit;
}

$account_id = substr(password_hash($email . $password, PASSWORD_BCRYPT), -40);
$hash_pass = password_hash($password, PASSWORD_BCRYPT);

echo $account_id;
echo $hash_pass;

//
// on traite la variable first_name
//
$first_name = $_POST['first_name'];

if(empty($first_name) OR strlen($first_name) > 30);
{
   $first_name = NULL;
}

//
// on traite la variable last_name
//
$last_name = $_POST['last_name'];

if(empty($last_name) OR strlen($last_name) > 30);
{
   $last_name = NULL;
}

//
// on génère une clé pour l'api
//
$api_id = random_1(40);
echo $api_id;

//
// on récupère la date du jour
//
$creation_date = date('Ymd');

//
// on se connecte à la base de données
//
require_once 'sqlconnect.php';

$sql = 'INSERT INTO accounts VALUES ($first_name, $last_name, $email, $hash_pass, $account_id, $creation_date, 1, $api_id)';
$prepare = $bdd ->prepare($sql);
$res = $prepare ->exec($sql);

?>