Once you have a few variables you can make operations with them:

```
$base = 20;
$height = 10;
$area = $base * $height;
```

The `*`

I used to multiply $base per $height is the multiplication operator.

We have quite a few operators, let’s do a quick roundup of the main ones.

To start with, here are the arithmetic operators: `+`

, `-`

, `*`

, `/`

(division), `%`

(remainder) and `**`

(exponential)

We have the assignment operator `=`

, which we already used to assign a value to a variable.

Next up we have comparison operators, like `<`

, `>`

, `<=`

, `>=`

. Those work like they do in math.

```
2 < 1; //false
1 <= 1; // true
1 <= 2; // true
```

`==`

returns true if the two operands are equal.

`===`

returns true if the two operands are identical.

What’s the difference?

You’ll find it with experience, but for example

```
1 == '1'; //true
1 === '1'; //false
```

We also have `!=`

to detect if operands are *not* equal:

```
1 != 1; //false
1 != '1'; //false
1 != 2; //true
//hint: <> works in the same way as !=, 1 <> 1
```

and `!==`

to detect if operands are not identical:

```
1 !== 1; //false
1 !== '1'; //true
```

Logical operators work with boolean values:

```
// Logical AND with && or "and"
true && true; //true
true && false; //false
false && true; //false
false && false; //false
true and true; //true
true and false; //false
false and true; //false
false and false; //false
// Logical OR with || or "or"
true || true; // true
true || false //true
false || true //true
false || false //false
true or true; // true
true or false //true
false or true //true
false or false //false
// Logical XOR (one of the two is true, but not both)
true xor true; // false
true xor false //true
false xor true //true
false xor false //false
```

We also have the *not* operator:

```
$test = true
!$test //false
```

I used the boolean values `true`

and `false`

here, but in practice you’ll use expressions that evaluate to either true or false, for example:

```
1 > 2 || 2 > 1; //true
1 !== 2 && 2 > 2; //false
```

All of the operators listed above are *binary*, meaning they involve 2 operands.

PHP also has 2 unary operators: `++`

and `--`

:

```
$age = 20;
$age++;
//age is now 21
$age--;
//age is now 20
```

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