A recursive function is a function which calls itself to repeat, again and again until the final condition arrives.
Recursion can be thought of as an alternative to iteration — that is, for and whileloops.
This program will be printing the number from one to Five, In this Code, the function used to print the number is the nameprintNumber()and the $i is the name of the variable that will help the printNumber()function get some value that will eventually lead to invoking it.
When the value stored in it exceeds the value of five, the condition that must be satisfied to execute the program further will go false, and the program will be terminated.
The function with the same name has been called within it that is used to implement the mechanism of factorial in the program.