I spun up the simplest example I could think of to illustrate a recursive function to a PHP beginner the other day, and I thought I’d share. I often don’t post really basic content but I should – people are beginning to be beginners all the time, after all!

### Factorials

Factorials are a very easy maths concept. They are written like `5!`

and this means `5 * 4 * 3 * 2 * 1`

. So `6!`

is 720 and `4!`

is 24.

`6!`

is the same as `6 * 5!`

, or `6 * 5 * 4!`

… and this is where the recursive functions come in. Continue reading