Write a PHP program to compute and print sum of two given integers (more than or equal to zero

 80) {
        echo "overflow\n";
        continue;
    }
    $arr = array_fill(0, 81, 0);
    $a = sprintf('%081s', $a);
    $b = sprintf('%081s', $b);
    for ($j = 80; $j > 0; $j--) {
        $n = $arr[$j] + $a[$j] + $b[$j];
        if ($n >= 10) {
            $arr[$j] = substr($n, 1);
            $arr[$j - 1] += 1;
        } else {
            $arr[$j] = $n;
        }
    }
    $result = preg_replace('/^0+(\d+)$/', '$1', implode('', $arr));
    if (strlen($result) > 80) {
        echo "overflow\n";
    } else {
        echo $result, PHP_EOL;
    }
}
?>