A curly quote (’) turns into ’ when submitted in a form

Question

When users submit a form on my site a curly quote (’) turns into ’, and an em-dash turns into —.

The form page contains this code that store the details to the MySQL Database:

$serializeArray = serialize($itemDetails);
update_option('art_'.$latest_order_id,$serializeArray);

The thank you page that extracts the information from the database and sends the details by email contains this code:

$serialized_array = get_option('art_'.$_GET['id']);
$itemDetails = unserialize($serialized_array);

I have the Content-Type set to UTF-8 in my tag. The MySQL tables are configured to use UTF-8.

When I check the details in the MySQL Database, the database contains the ’ character, NOT ’. The ’ appears when the data is extracted from the database.

What's the problem, and how can I fix it? Thanks!