PHP总结了从0到200的所有偶数

I tried to sum up all even numbers from 0 to 200 and I found 2 possible working ways, however the third method (the most efficient one) gives me a headache. Here's what I did so far:

First method:

$total = 0;
$number = 0;

while ($number < 200)
{
    if ($number % 2 == 0)
    {
        $total = $total + $number;
    }
    $number++;
}

echo $total;

Second method:

    $total = 0;
    for($number = 0; $number < 200; $number+=2) 
    {
        $total += $number;
    }
echo $total;

Third method (can't get it to work)

echo array_sum(range(1,200,2));

How should I change my last method so that it works as intended?

Edit: Seems that none of the methods work: the output should be 10100 but it is 9900 for the first two methods and 10000 for the third.

You need to use

echo array_sum(range(0,198,2));

or

echo array_sum(range(0,199,2));

Its because the above function will sum up the values upto 200 whereas within your while and for loop will count upto 198 only as you have specifically defined

$number < 200

begin from 0 but 1

echo array_sum(range(0,200,2));

result 10100

In the two methods that you tried, you have a condition that the number should not exceed more than 200. I also used the same scenario here.

echo array_sum(range(0,199,2));

Gives the expected output of 9900.

But the Correct answer is 10100.

To get 10100, We need to replace 199 with 200.

The formula (Mathematically)

2+4+6+8+10+..............+198+200 = 2(1+2+3+4+5+.....+100)

= 2 ((100*101)/2) (Formula: n(n+1)/2; n is the last term)

= 100*101

= 10100