Get country full name with PHP

Hi,

I use Address Field 7.x-1.2 on a Drupal 7.43 web site.

I need to print the address components (thoroughfare, postal code, city, country) with PHP in a Display Suite code field.

I can't manage to print to country full name. The following code prints the country code :

$adresse = $payeur->field_user_adresse2['und'][0]['thoroughfare']."
";
$adresse .= $payeur->field_user_adresse2['und'][0]['postal_code'] . " " . $payeur->field_user_adresse2['und'][0]['locality']."
";
$adresse .= $payeur->field_user_adresse2['und'][0]['country'];

Is there a way to achieve this ?

Thx in advance for your support.