PHP | Fibonacci Series

The Fibonacci series is a series of elements where, the previous two elements are added to get the next element, starting with 0 and 1. In this article, we will learn about how to generate a Fibonacci series in PHP using iterative and recursive way. Given a number n, we need to find the Fibonacci series up to the nth term.
Examples:

Input : 10
Output : 0 1  1 2 3 5 8 13 21 34

Input : 15
Output : 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 

Method 1: Using Recursive way
Recursion is a way where we repeatedly call the same function until a base condition is matched to end the recursion.

<?php
// PHP code to get the Fibonacci series
// Recursive function for fibonacci series.
function Fibonacci($number){

    // if and else if to generate first two numbers
    if ($number == 0)
        return 0;
    else if ($number == 1)
        return 1;

    // Recursive Call to get the upcoming numbers
    else
        return (Fibonacci($number-1) +
                Fibonacci($number-2));
}

// Driver Code
$number = 10;
for ($counter = 0; $counter < $number; $counter++){
    echo Fibonacci($counter),' ';
}
?>

Output:

0 1  1 2 3 5 8 13 21 34

Method 2: Using the iterative way
At first, we initialize the first and second number to 0 and 1. Following this, we print the first and second number. Then we send the flow to the iterative while loop where we get the next number by adding the previous two number and simultaneously we swap the first number with the second and the second with the third.

<?php
// PHP code to get the Fibonacci series
function Fibonacci($n){

    $num1 = 0;
    $num2 = 1;

    $counter = 0;
    while ($counter < $n){
        echo ' '.$num1;
        $num3 = $num2 + $num1;
        $num1 = $num2;
        $num2 = $num3;
        $counter = $counter + 1;
    }
}

// Driver Code
$n = 10;
Fibonacci($n);
?>

Output:

0 1  1 2 3 5 8 13 21 34