How can I check to see if the current user has an an order in checkout?
Preload $user variable.
Remove those / at the end of each url.
Add a semicolon at the end of each PHP line.

global $user;
if ($order = commerce_cart_order_load($user-&gt;uid)) {
  drupal_goto('checkout');
}
else {
  drupal_goto('someotherpage');
}