# PHP: Operators

Let's learn some important terms before moving forwards. An operation sign like `+`

is called an **operator**. It's just a symbol that produces a certain operation. Later you'll learn that there are other operators in PHP, than just arithmetic ones.

```
<?php
print_r(8 + 2);
```

In this example `+`

is an **operator**, and numbers `8`

and `2`

are **operands**.

In case of addition there're two operands: one on the left, one on the right from `+`

. Operators that require two operands are called **binary**. If you skip at least one operand, like so `3 + ;`

, the program will exit with an error.

*There are also unary operations (with one operand) and even ternary (with three operands)!*

Symbols *+* and *-* are used not only as operators. As far as negative numbers are concerned, the minus sign becomes part of the number:

```
<?php
print_r(-3); // => -3
// The same as 4 - 3
print_r(4 + -3); // => 1
```

The plus sign can work in the same way:

```
<?php
print_r(+3); // => 3
print_r(1 + +3); // => 4
```

## Instructions

Write a program that calculates the difference between `6`

and `-81`

, and prints the result to screen.

## Definitions

Arithmetic operator - addition, subtraction, multiplication, division.

Operator - special symbol that creates an action. For example,

`+`

creates addition.Operand - that what is being used with an operator.

`3 * 6`

: here 3 and 6 are operands.Unary operation - operation that requires one operand.

Binary operation - operation that requires two operands.