# 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.

Please sign in with your GitHub account, this is necessary to track the progress of the lessons. If you do not have an account yet, now is the time to create an account on GitHub.