深入理解递归

function sum($n){
    if($n > 1){
        $tmp = sum($n -1) + $n;
        echo $n, ‘<br />‘;
        return $tmp;
    }else{
        echo 1 , ‘<br />‘;
        return 1;
    }

}

echo sum(5);

echo ‘<br />‘.‘=========================‘;

function sum2($n){
    if($n > 1){
        echo $n, ‘<br />‘;
        return sum2($n -1) + $n;
    }else{
        echo 1 , ‘<br />‘;
        return 1;
    }

}

echo sum2(5);