Chyba: Call to a member function prepare()

require_once('config.php');

$dsn = 'mysql:dbname=' . DB_DATABASE . ';host=' . DB_HOST . '';
$user = DB_USER;
$password = DB_PASSWORD;

try
{
$pdo = new PDO($dsn, $user, $password);
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

}
catch (PDOException $e)
{
die('Connection failed: ' . $e->getMessage());
} 

function insert_jock( $cas_od, $cas_do, $den_cislo)
{
    $sql_t = "insert into tmp (tmp) value ('$cas_od') "; 
    echo $sql_t;
    $dotaz_ins_vysetr = $pdo->prepare($sql_ins_vysetr);
    $dotaz_ins_vysetr->execute();
}

Dostanem chybu:
Fatal error: Call to a member function prepare() on a non-object in E:\XAMPP\htdocs\ambulancie\vloz_JOCK.php on line 322