/* ------------------------------------------------------------
getCountryName
Receives a 2‑letter ISO country code and returns the
corresponding country name.
Uses an associative array for O(1) lookups.
Input is normalized to uppercase to ensure consistent matching.
Returns null if the code is not found.
------------------------------------------------------------ */
function getCountryName(string $alpha2): ?string
{
// Static lookup table; extend as needed
static $countryMap = [
'CA' => 'Canada',
'CN' => 'China',
'DE' => 'Germany',
'FR' => 'France',
'GB' => 'United Kingdom',
'KR' => 'South Korea',
'IN' => 'India',
'JP' => 'Japan',
'US' => 'United States'
];
// Normalize input
$code = strtoupper(trim($alpha2));
// Lookup
return $countryMap[$code] ?? null;
}
/* ------------------------------------------------------------
Demonstration
------------------------------------------------------------ */
$codes = ['US', 'GB', 'FR', 'JP', 'ZZ']; // ZZ is intentionally invalid
foreach ($codes as $code) {
$name = getCountryName($code);
if ($name !== null) {
echo "$code → $name\n";
} else {
echo "$code → (invalid code)\n";
}
}
/*
run:
US → United States
GB → United Kingdom
FR → France
JP → Japan
ZZ → (invalid code)
*/
