What is recursion in PHP

Recursion is a programming solution in which a function calls itself. It is used to solve a variety of problems, all of which have in common a structure that contains repetition. Recursion can be useful when solving problems related to HTML and other repetitive structures such as JSON and XML.

function calcFactorial($num)

{

    if ($num <= 1) {

        return 1;

    } else {

        return ($num * calcFactorial($num-1));

    }

} 

echo calcFactorial(5);