Problem
https://projecteuler.net/problem=2
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.
Answer: 4613732
Solution
<?php
function euler_solution_002($upper)
{
$fib1 = 1;
$fib2 = 1;
$result = 0;
$summed = 0;
while ($result < $upper) {
if (($result % 2) == 0) {
$summed += $result;
}
$result = $fib1 + $fib2;
$fib2 = $fib1;
$fib1 = $result;
}
return $summed;
}
echo euler_solution_002(4000000);
?>