What potential issues can arise when setting cookie expiration dates in PHP?

Setting incorrect cookie expiration dates in PHP can lead to cookies not being stored or being stored for too long, impacting the functionality of your website. To ensure proper cookie expiration, always set the expiration date in the future using the `time()` function in PHP.

// Set cookie with expiration date in the future
$cookie_name = "user";
$cookie_value = "John Doe";
$expiration_time = time() + 3600; // expires in 1 hour
setcookie($cookie_name, $cookie_value, $expiration_time, "/");