$length = $_GET['length'];
$proto = $_GET['proto'];
$dead = $_GET['dead'];

$dict = file("wordlist/" . $length . "_letters.txt", FILE_IGNORE_NEW_LINES);

$exp = '/^' . str_replace('*', '\w{1}', $proto) . '$/u';
$words = array_filter($dict, function($v) use ($exp, $dead) {
    $dw = true;
    foreach (array_diff(preg_split('//u', $dead), ['']) as $d) {
        if (preg_match('/' . $d . '/u', $v)) {
            $dw = false;
            break;
        };
    }
    return (preg_match($exp, $v) && $dw);
});

$letters = [];
foreach ($words as $v) {
    foreach (array_diff(preg_split('//u', $v), ['']) as $w) {
        $letters[] = $w;
    }
}

$ret = ['words' => $words, 'letters' => $letters];
var_dump($ret);