In project Euler example 2 the question is very simple:

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.

Now to find a Fibonacci sequence

```
function fabonnaciNumber()
{
$a = 1;
$b = 1;
$sum = 0;
$c = $a + $b;
while($c < 4000000){
if($c % 2 == 0){
$sum += $c; // $sum = $sum + $c;
$a = $b + $c;
$b = $a + $c;
$c = $a + $b;
}
}
echo $sum;
}
echo fabonnaciNumber();
```

In this function, the variable **$a** is initialized with value 1 and **$b** is also initialized with the value **1**. We need to store the sum and make sure the value is not exceeding 4000000. so we have to create a new variable called **$sum** initialized with value **0**. Create another variable called **$c = $a + $b;** which holds the sum value of **$a** and **$b**.\

Now run a while loop that has a maximum iteration value of 4000000. check if the number is perfectly divisible by 2 then sum the value of $c into $sum and update the value of **$a, $b,** and **$c**.