. * * To disable strict typing, comment out the directive below. */ declare(strict_types=1); function buildLetters(): array { $letters = []; $base = ord('A'); for ($i = 0; $i <= 25; $i++) { $letters[chr($base+$i)] = TRUE; } return $letters; } function isPangram(string $string): bool { $letters = buildLetters(); foreach (mb_str_split(mb_strtoupper($string)) as $letter) { unset($letters[$letter]); } return empty($letters); }