## PHP Examples Tutorial Index

Learn how to implement the Fibonacci series in PHP. This tutorial explains how to code a PHP Fibonacci series with examples. Understanding this concept will improve your understanding of recursion and loops.

## What is a Fibonacci Series?

The Fibonacci series is a numerical sequence in which each number is the sum of the two numbers that come before it. Typically, the series begins with 0 and 1, following this pattern:

``0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, ...``

## Generating the Fibonacci Series in PHP

There are two main ways to generate the Fibonacci series in PHP: using a for loop and using recursion.

### Using a for Loop

The following code shows how to generate the Fibonacci series up to the 10th term using a for loop:

Example:

``````<?php
\$first_num = 0;
\$second_num = 1;
\$n = 10; // Number of elements you want in the series
echo "Fibonacci Series: \$first_num, \$second_num";

for(\$i = 2; \$i < \$n; \$i++) {
\$next_num = \$first_num + \$second_num;
echo ", \$next_num";
\$first_num = \$second_num;
\$second_num = \$next_num;
}
?>``````

Explanation:

In the above example, the variables `\$first_num` and `\$second_num` are initialized to hold the starting numbers of the Fibonacci sequence—0 and 1, respectively. The variable `\$n` sets the desired length of the series. Within the `for` loop, `\$next_num` is calculated as the sum of `\$first_num` and `\$second_num`. These two variables are then updated in preparation for the next iteration, ensuring the series continues to generate accurately.

### Using Recursion

The following code shows how to generate the Fibonacci series up to the 10th term using recursion:

Example:

``````<?php
function fibonacci(\$n, \$first_num = 0, \$second_num = 1) {
if(\$n == 0) {
return;
}
echo \$first_num . ", ";
\$next_num = \$first_num + \$second_num;
fibonacci(\$n - 1, \$second_num, \$next_num);
}

\$n = 10; // Number of elements you want in the series
echo "Fibonacci Series: ";
fibonacci(\$n);
?>``````

Explanation:

In the above example, the `fibonacci` function primarily requires one argument, `\$n`, which specifies the length of the Fibonacci sequence to generate. The other two arguments, `\$first_num` and `\$second_num`,  initialize and update the sequence. These are set by default to 0 and 1, the starting numbers of the Fibonacci sequence. The function uses recursion to call itself, decrementing `\$n` and updating the sequence numbers until `\$n` reaches zero, thereby completing the series.

## Conclusion

Generating a Fibonacci series in PHP is a straightforward task. You can use either a for loop or recursion based on your project's needs. Both methods explained in this tutorial are efficient and help you understand the core concepts of programming and PHP.