PHP Triangle
function triangle(array $a): int
{
    sort($a);
    $c = count($a);
    if ($c < 3) {
        return 0;
    }

    for ($i = 0; $i < $c - 2; $i++) {
        if ($a[$i] > 0 && $a[$i] > ($a[$i + 2] - $a[$i + 1])) {
            return 1;
        }
    }

    return 0;
}

This sorts the values and checks nearby triples, because a valid triangle only needs one local match after sorting.