PHP 7 Data Structures and Algorithms

Implementing Fibonacci numbers using recursion

In mathematics, Fibonacci numbers are special integer sequences where a number is composed from summation of the past two numbers, as shown in the following the expression:

If we implement this using PHP 7, it will look like this:

function fibonacci(int $n): int {     if ($n == 0) {     return 1;     } else if ($n == 1) {     return 1;     } else {     return fibonacci($n - 1) + fibonacci($n - 2);     } }

If we consider the preceding implementation, we can see it is a bit different from the previous examples. Now, we are calling two functions from one function call. We will discuss different types of recursions shortly. ...