Let's move on to a bit of arithmetic. The most common Math function you'll use is `round()`

. This function rounds floating point numbers (numbers with decimal points in them) up or down.

You can use `round()`

to round your number to an integer, or to round off complex floating point numbers to a specific number of decimal places. This is accomplished by passing a second, optional parameter to `round()`

, telling it how many decimal places you want the number rounded to.

Here's an example:

```
// Round pi down from 3.1416...
$round = round(M_PI);
print $round; // prints 3
// This time, round pi to 4 places
$round_decimal = round(M_PI, 4);
print $round_decimal; // prints 3.1416
```

*NOTE:* `M_PI`

is a PHP constant that is equal to *pi*.