Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

`1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...`

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

Our second problem gives us a sequence which our teachers forced us to learn at the primary school. The lovely "Fibonacci sequence".

Here is an option to solve this problem in PHP:

```
$n1 = 1;
$n2 = 2;
$n3 = $n1 + $n2;
$sum = 2;
while ($n3 < 4000000) {
$n1 = $n2;
$n2 = $n3;
$n3 = $n1 + $n2;
if ($n3 % 2 == 0) {
$sum += $n3;
}
}
echo $sum;
```

We already know the first three numbers which create us a pretty nice start point for our tiny calculator. So we define the first three numbers and according to our "hard-coded" data, we define the `$sum`

. The important point is to keep in mind that only the *even* numbers should be added to the `$sum`

.

In the `while`

loop, we check if the next number of the sequence smaller than 4 million. If it is, we are good to go and check if our second condition passes.

We know that the `modulus`

(`%`

) of even numbers to `2`

should result `0`

. So we write out `if`

statement and all done!

**Execution time: 0s**