PHP compare dates to determine if one is expired

//Define the album date in a variable
$albumDate = 2012-11-01;
//Call to function
albumExpired($albumDate);

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//  Show expired albums
function albumExpired($expiry){
  // Find todays date.
  $today = date("Y-m-d");
 
                //Change date into a string
  $todaysDate = strtotime($today);
 
                // Change the album date into a string
  $expiryDate = strtotime($expiry);
 
                // compare the two dates (strings)
  if ($expiryDate<$todaysDate){
   return 'Expired';
  }else{
   return 'Not Expired';
  }
}